That makes sense, I suppose. Personally, I like having some historical (or real-world mythological) elements in my fantasy, because it provides a sort of touchstone connecting it with the reality I know. For me, starting with something real and then modifying it based on the changes that would be made by magic/highly advanced technology/alien space bats results in more verisimilitude than creating one that's totally unconnected to ours, but which happens to have humans and a lot of Earth's wildlife. Different strokes for different folks, I guess.