Because they are picky and hard to get in to. To a VC who has very few other ways to asses you, having something in you past that singles you out as someone wh

Because they are picky and hard to get in to. To a VC who has very few other ways to asses you, having something in you past that singles you out as someone who has already cleared a highly selective process means you are more likely to be the kind of person who succeeds. Nothing to do with Google's own products. Any other club similar difficult to get into will convey the same signal. It's a crude signal, but it's a signal.