AirBNB raised $1B and Stripe $600M. Just a guess but terms would've been MUCH better if they'd done it in the stock market. Really puzzling why they didn't go public when markets were ripe, now YC is paying the price.
When you are Stripe big, what does YC do for you that you can't do with your own money printing machine? Aside from cash, there must be other advantages to having investors.