I'd like this because it would allow for animated gifs, and I'm not prepared to give those up forever without a fight. Nor do I want to be stuck with mushy jpgs forever, the file format that I hate most. Gravatars are just awful, and the last I checked they have to be some tiny size like 50x50 which means Xenforo would resize them upwards - right? (If so - bleah.)
Avatars are a big deal to people - the more options they have with them, the better. It makes no sense to give people a slick modern board that's more convenient in every other way, and then stick them with blurry muddy jpgs for their avatars. It's like giving someone a brand new high-tech laptop and forcing them to use dialup to get online.