I try to use as much free software as possible. You may have heard the term "open source" for what I call free software. Others and I don't use this term as it puts the emphasis only on one property of the software and not on the part that is most important to me: freedom. Free software means that you can use the software for any purpose, modify it and share the software, either in unmodified or modified form. I don't only use free software for moral or philosophical reasons, but also because there are numerous practical benefits. I may have some disadvantages or inconveniences by trying to not use proprietary or nonfree software. It may even prevent me from using certain hardware if it's not possible at all to use this hardware with free software. But many of the problems turn out to be issues only at first sight or are outweighed by the advantages of their free counterparts. You can check for yourself if the software you are using is free software. Check the license it was published under. It should be one of the free licenses.
Giants
Free software is the future. There are thousands of free software developers around the world and you are really standing on the shoulders of giants when you are using free software. Companies or individuals that produce proprietary software cannot compete in the long run with these development efforts of a sharing and cooperating community. I use Debian as operating system on my PC, laptop and servers. Debian has around a thousand developers. Nearly all of these developers don't actually develop the software they maintain, but they fix issues here and there and make sure that everything works together nicely. Debian does not only offer you the base system like Windows or Mac OS does, but it already includes nearly all the software you need, more than 43.000 individual software packages in total. A common myth is that free software is only based on the efforts of hobbyists, but in fact a lot of free software developers are professionals that make their living by creating free software and there are quite some companies that make money from developing free software or providing support for it. For example, more than eighty percent of the several thousand Linux kernel developers get paid for their work on the kernel. The Linux kernel is the core of a GNU/Linux operating system like the one that is offered by Debian.
Security and privacy
Real security and privacy is only possible with free software. Free software is the prerequisite to have security and privacy in our computing. Only free software can be fully vetted by anybody. Security researchers can independently audit the software and share their results. Everybody can work on improving the software and make it more trustworthy. And the users can ensure themselves that the software they are running is actually doing what it's supposed to be doing. Developers of nonfree software often solely rely on security by obscurity. They think that if they hide the source code or, in general, information on the inner workings of the software, then nobody can find vulnerabilities or backdoors in the software. This behavior is comparable to children who cover their eyes and think they are invisible. People still have a lot of ways to identify security issues in the software and steal your data or listen in on your laptop's microphone. Features that harm the users won't survive in free software. Someone will get rid of them and the users will start to use the version of the software that has these antifeatures removed.
You don't have to be a software developer or a security expert. Alongside the free software developer community comes a huge community of very nice people that will help you with numerous tutorials and documentation. You will most certainly also find someone who answers your questions directly. Even if you have no interest in any of the technical details, you will find plenty of support to use your computer securely and retain your privacy.
My understanding of privacy is that I can decide what information I share with whom. My goal is not to run around as a huge question mark, my goal is to be in control of my own data and in the broader sense of my own destiny. Only free software has the possibility to guarantee this control in the digital age of computers. Even if you don't value your own security or privacy for whatever reason, you should acknowledge the need of others. If someone asks you for a private conversation, you will probably step aside, lower your voice and listen to what the other one has to say. The same goes for mail exchange, the chat software you use with your friends or the online service you use to exchange files with others. If some of your peers care for their privacy or security, then you should respect that. It won't hurt you to do something to increase the level of your privacy and security, at least for the sake of others.
There is a technological area where I especially want to see the use of free software: medical devices. If my well-being depends on the well-functioning of a device like a pacemaker or an operational tool for a surgeon, then I want to have a look at the source code that runs on that device. I want to show the source code to experts and they should be able to tell me if the software works correctly. If there is a way to update the software on the device and if the software running on the device needs to be improved, then I should have the right to let someone do the update. Companies that produce medical devices should be held to the highest possible standards of quality assurance. Publishing the software for medical devices as free software should be a prerequisite of the quality assurance. We can't solely trust the companies because the interests of the customers is not always aligned with the business interests of the companies. If source code is not published under a free software license because certain persons in charge think that this may decrease their revenue, then the well-being of the patient is neglected merely because of the possibility that someone gets more money.
Our devices are getting more and more powerful. And the need for security actually grows at an even faster rate. A few years back, we were wondering if someone could access our files and manipulate the software on our PC if we connect our PC to the Internet. Then we feared that we were watched through our webcam. After that, smartphones became a thing and we started to carry around wiretaps that can also track our locations. As security is more and more lacking on these devices, the gap between increased abilities of these devices and the need to secure the devices is becoming bigger and bigger. Especially on mobile devices, the lack of security updates or of any effort to make them trustworthy is sometimes outright horrifying. This is one reason why I try to contribute to the Replicant project.
But smartphones are not the end. We are more and more entering the reality of the buzzword of nightmares: the internet of things. Why not connect everything to the Internet? At some point in the future, almost every car will have some sort of remote control. There's a real possibility that you will buy for your parents a robot that will help them in the household when they get older. So the thread of being passively watched, listened to or tracked will be extended by the thread of being actively physically harmed. There are already numerous reports about the lack of software security in cars and security researchers were able to remotely control cars. I don't want to live in a world where some madman can sit on his bed, sip his coffee and occasionally crash my car or choke my parents to death with the robot I bought for them. With free software, we are be able to see what functionality the devices have, how its security can be improved or more simple: We would be able to disable a certain functionality like remote control if it's just ridiculous to have that functionality in the first place.
Our world and our society is not getting improved by people who say that everything is alright. People who call out the issues at hand and nag us about them are doing the first step to change something for the better. Actually doing something to solve our problems is the next step. Activists are doing all of this. Whistleblowers provide us with the information. Investigative journalists research the issues. All of these groups highly depend on free software for their daily tools. Free software makes it possible for them to evade surveillance of authoritarian or corrupt governments. For some of them, security or privacy issues in the software they use can cost them their lives. I see the striving for more transparency and the opposition to censorship as one of the biggest tasks for our generation. If we all use free software, then it will be really difficult for evil organizations to even single out the activists or whistleblowers among us. But doctors and lawyers should demand free software, too. How should they be able to guarantee the privacy of their clients otherwise?
Sustainability, education and research
Free software makes sustainability possible. You can run recent software on quite old hardware because it's technically possible and there is no company hindering you from doing that because they think that this may be bad for their business model. And in the same way, you can be sure that you will be able to access your data or your work for many years to come. Many people cannot afford to buy new hardware every two years. With free software they can use their hardware without any issues for up to fifteen or more years and still benefit from new features and security updates. Using our hardware for as long as possible is also a way to protect the environment. Normally, we cannot ensure that the manufacturers adhere to current standards to protect the environment or that they respect their workers' rights and don't exploit them. A longer utilization time and buying second-hand hardware are ways to not support abuse of workers and to conserve our environmental resources. We are living in a society that promotes consumerism. Free software helps to gain a new perspective on these issues, also by encouraging the users to contribute.
Free software should be mandatory in education and research. Especially if I spend a lot of time learning to use certain software or if I for some reason strongly depend on a piece of software as part of my work, then I want to be able to use that software for any purpose and for as long as I want. Additionally, I want to share that software with others and fix issues or ask others to fix problems with the software so that I can continue to use it. Only in this way, the knowledge from learning to use the software is not lost and everybody can fully benefit from the software. Researchers should use free software and they should publish the code they write as part of their research as free software. This way, it's possible to reproduce their results and to build upon them.
Children in school shouldn't use nonfree software that hides information from them, collects their personal data and makes them dependent on the developers or the companies behind the software. Many companies that develop nonfree software give their software away at no cost to schools and universities. Later on, they can extort ridiculous amounts of money from the graduates or the employers they work for so they can continue to use the nonfree software they just learned to use with a lot of effort. In the case that the companies go bankrupt and the software development ceases, the acquired knowledge about the software would be completely lost. With free software the source code of the software is available, so we can continue to maintain the software for ourselves or anybody else can pick up the development of the software so we can continue to use it. Free software promotes collaboration and encourages to take a look inside to see how everything works. In the sense of open access to knowledge, free software allows students and others alike to discover how a computer works and what happens if we change some parts of the source code. I personally only started to enjoy using a PC in order to get work done (especially coding) as soon as I started to deliberately use free software. Meeting others of the community at gatherings like FOSDEM or the Chaos Communication Congress increased my enthusiasm.
I think that free software will gain a lot more traction as soon as more people will not only value the functionality and ease of use of the software they use, but also security, privacy, sustainability and societal effects. I hope that I could give you a better understanding of these effects. All these benefits of free software stem from the freedoms we get by using free software. If you believe in a free society, then I hopefully convinced you that free software should be a part of it. We should demand these freedoms as rights for ourselves. If we don't do this, then others will be in control: governments, companies or the machines themselves.