You ever seen those scenes in the Matrix where you have the main characters and then you have everybody else who are humans like everyone else in the Matrix but they just dress normally and have no noticeable features or stand out in any way in the movie
I used to have an avatar at the old place. I had the Great Deku Tree, and before that, Meredy from Tales of Destiny II / Eternia:
But I just didn't feel like figuring out what avatar to use when we moved here, so I've just stayed avatar-less. I'm not super active here or a particularly notable person on the site, so I don't feel like I need one, anyway.
An actual answer is that a lot of people who browse the forum at work or have really low bandwidth have images and avatars turned off, so there is no reason to set one.
Quality of a post isn't determined by what picture is next to it. I wouldn't have bothered putting one up, but some people can get surprisingly pissy about it.