What we call mythology for ancient Greeks was their history. You can compare it with religions but it was more like history. If a person claimed that Hercules was his ancestor that could justify holding a leading position in many Greek cities. read more
You may ask what purpose served Plato’s hostility against the myths and oral traditions of the ancient Greeks, but not what purpose the myths served because myths are memories made into stories. Nobody created the myths, either in ancient Greece or anywhere else. read more