If you're very important, like the guy who invented the Pringles can, you probably know what you want to be remembered for.  The rest of us are still thinking.  We're also thinking about how easy it is to get stuck in a cycle of living for everyone but yourself.  Burnout is real, and it rarely ends well.  And just because you're not Pringles Can Famous doesn't mean you don't have an identity outside of what you've done for the world.