An epigraph can do a lot on the page, too, for the reader: contextualize, mood-set, jar, subvert
Good point. I hope Genette covered some of these in his essay. If poetry is in part an exercise in empathy, it’s not unreasonable to suppose that poets have these reactions very much in mind.
I think you’re right about epigraphs tending to drop out in revision — that’s been my experience, too. I also used to fonder of them when I was younger and less sure of myself as a poet. I wouldn’t characterize my reaction to other poets’ overuse of epigraphs as annoyance, exactly — I guess most of the time I see them as readily ignorable. (Which kind of contradicts what I said about epigrams being intrinsic to Cibola, but that represented an extreme rather than a typical example of epigram usage.)