Avatars are, In my opinion, the face of the poster, and I generally view people who have hundreds of posts without and avatar to be lazy. It's not a personal thing, I just can't understand why they wouldn't unless they can't be arsed or don't know how.
The first forum I ever joined had a large user base, frequent posters, and lots of people who enjoyed creating signatures. I learned to do simple editing of images to make signatures, and found myself spending hours simply creating magnificent signatures; so many, in fact, that I would change it damn near every day (which could understandably get annoying to some people).
I tend to identify posters by their avatar, so I often lump together people with the blank-face avatar as being the same person(s) as I quickly read through the forums (I don't have much time usually so I don't take the time to read forum names, lol).