I lost count of the many reasons why I use Linux. I've started using it out of curiosity. Back in 2004 when I was a bored teenager with no friends I started dabbling around with it. I spent most nights in the summer of 2005 slightly drunk, trying to configure Debian after removing all packages that didn't seem too important at first. It was an interesting experience to say the least. Thinking back this might have been the first time I've really dug into a system. In a way it's my earliest memory of hacking something. I practically ditched Windows at that time, although I kept it around for some specialized applications (audio production stuff). I solved the whole gaming problem by just not gaming anymore. Eventually I ended up buying a console in 2008 or so I think. I used that until 2012 when I first tried Steam on Linux. I also played some FOSS games of course.
I sometimes get reminded of the advantages that Linux has, because sometimes I tend to forget them. It's normal for me to have easy updates, incredibly stability, etc. I'm shocked when I'm confronted with the utter mess that is Windows. I'm appalled at how horrible even simple configuration tasks can be on Windows, which I could do with just a handful of lines on the CLI on Linux.
Well, I ended up studying computer science, so Linux really is a perfect match for me. All the software I use is free, and I can look under the hood as much as I want. I have the power to actually command my computing just how I want it, I'm not chained to what some guy in some management board thinks I should be doing with my software. I've got absolute freedom. When I started using Linux, I didn't care much about this. I was a broke teenager, all I cared about was that it was free as in free beer. In the meanwhile, I've not only come to appreciate the concept of free software, but really believe that this is the only ethical way. After all, information should be free.
So I use Linux because it's simply the overall best system out there. Yes, some BSD might be more secure, but all things considered Linux is still the better system.