Well, here we hit the fact that while I'm in Pride and Prejudice fandom and am aware that people sell their fanfic I'm not in much contact with the parts of the fandom that do that. My attitude comes more from fanart fandom and webcomics, where it's perfectly normal to keep the stuff you sell viewable for free online as an advert to make people buy more. So if I published my fic I would totally keep it available on the archive, and until reading your comment it didn't occur to me that some people would remove it by default. I can see how that would be a problem.

EDIT: Also, from your other comment: I realise it's not normal to keep novels online for free after they're published, and choosing to do so definitely limits one's publishing options. But it's not impossible or unknown. I must admit, I really haven't looked into the logistics (beyond looking into zine-ish publishing of my original comics) but afaict self publishing can be fairly effective for niche works and there's no publisher there to complain about putting stuff online for free. Cory Doctorow makes all his books available for free online, too, though he had the advantage of being famous to start with.

(I realised today that some of my frustration with this discussion is coming from the fact that as a fanartist with art on the AO3, and knowing that fanart is going to be fully supported by the AO3 in the hopefully near future, I apply any argument people make to fanart and fancomics as well as fic, but most people seem to only be thinking about fic)