Having a purpose sounds like a bit of a tall order. You're specifically put on Earth to do this and this? You mean that has to come first, before everything else? And I don't necessarily get to pick what that purpose may be? No thanks.
If you find one, and it suits you, beautiful. Some people need and want that kind of direction/structure in their lives. I don't want a purpose. I've got too many other things I want to do.