few games that don't have them are specifically structured to not need them.
Mounts are such a common thing that the existence of them in a game isn't enough to make the game stand out, and in the crowded MMO market, standing out is exactly what a game needs to do. So a logical step for many developers is to try and come up with a mount that is unusual in some way. They'll often strive to come up with the quirkiest, funniest, coolest, fastest, anything-est mount, just as long as it doesn't get lost in the herd.
So what's the best one you've come across? Did it have some ability or feature that caught your eye, or did it just look cool? Click the little button and let us know!