Matter of fact, I was using linux when I was 12! Actually installed ubuntu myself.
However, I wasn't into it to the extent that I could follow the linux distro culture. Don't even remember the version now; must have been 10 or 11.
There was also the fact that I had limited access to the internet in the early days (that's just how it was in India).
I was just sick of trying to make pirated software work (including windows), so was looking for something I can just download and run.
I do remember that I liked how easy it was to install games, compared to my windows desktop.
Only now, that I am familiar with software development cycles do I understand how stupid it is of Ubuntu to discontinue fully featured, polished software.
For example, Mac has changed so little over the years (haven't personally used it much), which probably is the reason why it's so much more mature as compared to linux DEs...
When I was 12, we were messing up with the Amiga on geek friend's house, ProTracker had just been released, playing Defender of the Crown on the school PCW computers and doing Z80 programming on my own Timex 2068. :)