The Graywolf Press blog makes the case.
From the piece...
Author photos, collectively, aren’t as bad as that, but they, too, testify to depressing bias, often unacknowledged or even unconscious, in the way that book publicity works. A few months ago I saw the first-time author of a literary novel reviewed in a large-circulation journal alongside a photo of the author, who was posed like an odalisque, that took up as many square inches as the review. Maybe the review came in short and the editor needed to fill up space, or maybe the editor was paying homage to a talented portrait photographer, but the effect was that (as with some pop stars) the novel had received this kind of attention principally because its author was hot.
The sentence you have just read says nothing about the gender of that author, but if you’ve made an assumption about that author’s gender, you probably got it right; if you made an assumption about that author’s age, within about ten years, you probably got that right, too; and the fact that you did tells you what I dislike most, what makes me angry (rather than just annoyed) about author photos in general, however happy I am with my own.