It should be possible upload a custom avatar to one's profile. I don't like to have to arrange to serve my avatar from elsewhere. Even if you don't want attachments in general -- which I think should be allowed -- 4K avatars are not likely to be a problem
that's 1.4 gigs just in custom avatars as of now
yea its not THAT much in modern terms of space, but its darn near the size of hard drive I had 10 years ago for silly little pictures that most people never pay attention to
besides you don't HAVE to have one, but if you want one they give you the option (besides there are free avatar hosting things like gravatar, so you don't even have to use your own space)