Ask PG: How do you find personal fulfillment by helping startups?

Sincere question, no troll here. I love the tech/startup scene and struggle with this all the time. As someone who obviously doesn't think there's any afterlife, why are you spending a defining part of your career helping create (even) more startups? I'm assuming it's not for the money so you must get plenty of personal satisfaction out of it. But it's one of those "is this the absolute best problem I could spending my time on?"