Use? To burn money in a very expensive hobby, looking at the pretty scenery outside.
It also gets you entry into a relativly exclusive club - meeting some very experienced and interesting individuals. Its also great fun as a challenge to yourself to constantly stay ontop of a subject and skill (things never stay static in aviation).
Often it is a stepping stone to move into comercial aviation.
Very rarely, someone will use their PPL for something practical (like commuting to an in accessable location, often over water or an in accessable area).