Some people commute on a unicycle too. Anything goes dude. Hey if you want to ride on a sweet Kona Supreme Operator... that's cool too. Should make short work of the Mount Royal steps!
Lots of folks ride hardtail to work. You use what you got. Then the addiction kicks in and you end up with something more balanced to your riding condition. Most folks' commute on paved roads or packed trails. So riding efficiency is a consideration.