I know it seems like poor business, but I think it's well-suited to young entrepreneurs:
- It lets them focus on their presumed competency of making something people want. They don't know much about running a business, selling on a day-to-day basis, managing employees or even doing business development.
- It proves the product's worth quickly. A good business with a lousy product is not worth much, so focus on getting a great product first. You can criticize PG's "internet companies don't die from overpopularity" as a business model, but it's correct in practice.
- It tends to maximize the advantages of young founders: motivation, risk-taking ability and fresh analytical approaches.
- It fits with the life investment strategy that says that you take risks for large gains early in life as you build up your earning potential. Sure, young founders are undervalued, but even if they were properly valued they should still go for it.
That said, YC still does some stuff that isn't in that exact mold.