If, as Picasso said, art is the lie that tells the truth, it is hard to explain why artists evolved in the first place. Why would there be any evolutionary benefit in a subset of humans who spend their time telling lies in order to reveal truths? It is obviously more direct and efficient to tell a truth in order to reveal a truth.
One possible explanation: artists are an immune system against stereotypes. You can find an instance of any stereotype, whether it is a nasty stereotype or a flattering one, especially if you don't look very deeply. The problem with stereotypes is not that they represent pure fictions, but that they severely overgeneralize from genuine facts.
In other words, every stereotype represents a truth which tells a lie. Lies which tell the truth balance them out.