when i first joined up, i thought that would be a good idea also. but i'm a moderator on another board that allows you to upload your avatars. one big thing we ran into was people using "mature content" for avatars. it's been a real pain. that might be one reason...along with space/bandwidth issues.
Fitch is almost spot-on. It is not so much a space or bandwidth issue, but rather due to some people uploading "questionable" avatars. Uploading of avatars directly is no longer available due to that abuse.
Most likely, after the next software update, it will be available, but only to Members.