Why would they? They are buying into these companies at a $2m valuation which is absurd. It's a no-brainer move and almost nobody can rationally say no since YC is so powerful
How are they 'powerful'? Right now, it is a conveyor belt accelerator.
I used to be impressed to see a YC company, now that signal means nothing, there are so many of them.
If anything the signal is that the founders were too willing to give up significant equity for not a lot in return.
I keep reading these YC stories, but if you dig in, many of them had significant pre-seed funding and product history.