I for one can only think of the fallowing reason:
If you like playing 3d games, don't use BSD..... don't use linux..... use windows....
I was Windows user, then i switched to linux....
Then i tried FreeBSD.... and switched back to linux....
However in few days i used FreeBSD (about month) something changed in me...
And linux wasn't giving me satisfaction anymore....
So now i use FreeBSD
Reasons why not to use any particular system depends on individual itself...
I bet there are some creeps out there still using dos