Why Do Fiction Publishers Get So Uptight About Self-Publishing?

So we have a paradox – in science, a set of fields that purport to rigorously seek truth and prize quality above anything else, self-publishing initiatives are going over with nary a whisper of criticism. In fact, if anything, such approaches are proliferating, and are being embraced by librarians, scholars, and researchers alike. Yet in commercial publishing of fiction (aka, made-up stories), there is a major backlash. Why Do Fiction Publishers Get So Uptight About Self-Publishing?