A problem relevant to this case directly is why works can be under copyright after the passing of their creator. There shouldn't be an Andy Warhol Foundation licensing works. This is purely a rent seeking behavior. The money made from licensing Andy Warhol works does not fund further output by the artist. They are dead. You just have some randos extracting wealth from society for the privilege to use something that the creator profited from long ago. The work of dead artists should be in the public domain.