yes... the publisher does... or, more specifically, someone [usually an editor of some sort] who's working for the publisher does... that is, if not self/vanity-publishing, in which case the author does...
Actually, for my novel, I did in conjunction with my editor. But I am with a small press. Authors I know at larger presses (Bantam, St. Martin's, etc.) someone else creates them (editor/marketing)--sometimes with input from the author. Terry