Just like some other members here have mentioned, Theymos actually disabled it. I think back then animated avatars too were still in use and basically even newbies were able to upload an avatar back then but it made the forum messy. One basic thing I like about the forum is how simple it's interface is .

If everything is animated, the concept may seem fun at first however given the fact that this forum is a place for important and serious discussions, a flashy interface won't look cool.