But there *are* plenty of people who disdain feedback or criticism, saying that they write for themselves and that it doesn't matter if anyone even reads it.

That's not me at all. I write for myself, yes, in that I write what I'm interested in writing and am not swayed by someone who comes along and says I should have done this and this and he should have got together with that guy instead, etc., but if there were no one to read it, I'd probably spend my time on something else, because I wouldn't be able to motivate myself to actually write out the story (why should I if I'm the only one who's going to read it? Might as well keep it in my head and save myself the trouble).