Another example of schools proliferating without evidence: philosophy. Consider all the different schools of ethics which have sprung up: there's utilitarian ethics, deontological ethics, and virtue ethics, with vast numbers of sub categorizations under each school.

Philosophers are more susceptible to this failure mode because on many important philosophical questions, a standard if not unanimous approach is argue that the question cannot be answered by evidence. Modal logicians trying to do metaphysics, for example.