

I use the vi family of text editors in a CLI environment because it is part of the POSIX standard.
Even if nano is the default, vi will be there too, and I can just use that. Plus, if you know some basic vi commands, then you can get by without nano, and you don’t need to know nano to use it for basic stuff as it shows you the key combos.

Because it’s Free Software. Free as in freedom.
I think Haiku was the first FOSS OS I tried, but GNU/Linux was more usable.
I had used FOSS on Windows and Mac OS X before. Apps such as Firefox, and VLC. But didn’t really get it until I found and read the gnu.org and fsf.org sites.