Out of curiosity, I went back and looked at some of those old threads debating avatars (and there were many, some with hundreds of posts). I’ll link a few below if anyone’s curious. (It’s ironic seeing all the avatars displayed in an old thread about why we don’t have avatars).
Lynn_Bodoni’s post early in the first linked thread sums up many of the reasons against. A lot of people who opposed enabling avatars (and other images) did so out of fear of what might happen: people might post inappropriate images; bandwidth issues might slow down or break the board when displaying all those images; the boards could become cluttered and horrible-looking like other forums that people have experienced. Now that we’ve had avatars for a while, I think that, mostly, these fears have not been realized (which is not to say that things might not have been different a decade or two ago.)