We tell people we use Linux because it's secure. Or because it's free, because it's customizable, because it's free (the other meaning), because it has excellent community support...
But all of that is just marketing bullshit. We tell that to non-Linuxers because they wouldn't understand the real reason. And when we say those false reasons enough, we might even believe them ourselves.
But deep underneath, the real reason remains.
We use Linux because it's fun.
It's fun to tinker with your system. It's fun to change all the settings, break the system, then have to go to recovery mode to repair it. It's fun to have over a hundred distros to choose from. It's fun to use the commandline.
Let's say that again. It's fun to use the commandline.
No wonder non-Linuxers wouldn't understand.
The point with Linux fans is we use Linux for it's own sake. Sure, we like to get work done. Sure, we like to be secure from viruses. Sure, we like to save money. But those are only side effects.
What we really like is playing with the system, poking around, and discovering fascinating facts about the software that lies underneath it.