The size limitations for avatars is quite measly; but maybe large images take up too much space/memory on the forum?
Just saying, because I have noticed that many people don't have avatars, possibly because it's hard to find such small images,
in particular if you are looking for a particular theme. Can the file/image size be increased?

So people get some avatars as It's nice and imbues a sense of identity. I hate looking at lot's of blank avatars, feed me avatars...