The flip side of this analysis would be: YC and Sequoia prefer to fund kids because kids are easier to manipulate. Kids don't know how to read a contract or a term sheet. Kids don't know how to protect their own interests in their business when accepting funding. Kids don't know how to play hardball in negotiations.

Kids, in other words, are very easy to use as disposable resources.

(Indeed, with appropriate conditioning you can even convince them to believe that becoming a disposable resource is a sign of their Epic Founderhood.)

Someone who's seen peers get screwed over in previous gigs, or who's been screwed over themselves, is going to have learned a few things about how not to get screwed over the next time. So it's more profitable to deal with people who haven't learned those lessons yet. And once they have learned those lessons, you throw them overboard and replace them with the next batch of dewey-eyed innocents.