I think the real question here is "does it really matter?"
And to think I refused to write "Yes, I do care" at the end of that post, even though I was pretty sure that will be the reaction. The explaination is hard to be made without it sounding stupid, but I'll give it a go anyway.
As Philes stated recently, he (and quite a lot of other people) associate people with their avatars. For those who are just getting to know the forum and it's members it may be somewhat a bad thing that, as an example, they won't realise how one of the top posters, a guy named Xento, is the same guy as the faceless dude who posted here and there. The member list becomes much less useful when the first x posters lack their identities.
It's a flaw in the forum design. How minor it wouldn't be, it keeps the forum from being perfect. It's quite possible that only I'm such a perfectionist to be bothered with that reason, though. Also, let's combine this with the first reason. The problem is here for years (yet it didn't ever bother me enough to write about it), and it was here when I arrived. And when I did, I liked to lurk and view profiles of members, and usually the first one which crop out are top posters - here, the unique avatar possesing ones. First I thought that none of the top posters aren't active anymore, since all of the active ones had avatars. After a short time I realised that actually people having avatars don't have them in their profiles and for a long time though that avatars in profiles don't work at all and thought "Wow, this forum seems to be quite buggy". The impression was needless to occur. Also it made it slower for me to associate some posters (remembered by avatars) with their names and forum age (remembered via member list), like in the Xento example, so it propably makes it harder for newcomers as well.
Curiousness. I wonder what causes those avatars to not be shown. I wonder if it's a big technical issue or a small glitch which however didn't bother any admin enough to ever make him do anything about it.
We all care about meaningless petty issues that no one else gives a crap about. This one seems to be just one of mine.