There's talent in every region, and I think it should be a priority to figure out ways to unlock it without re-siting companies in SFBA and NYC, but it's worth noting here that YC's SFBA-centricity is not an outcome of their belief that there's no talent outside SFBA. It's the opposite: they assume they're importing that talent to the area.

The YC SFBA thing is about network effects from companies working in close proximity, and about the investor market (1) believing the same thing and (2) having themselves an even more significant network effect that keeps them all in the same area.