The most common reason I've heard is that the Valley is a terrible place to start a family.
I would imagine that the cost of housing plays a large part in that. Housing in the Silicon Valley/Bay Area is insanely expensive. Maybe not as bad as downtown Manhattan, but still insane by the standards of pretty much every other metropolitan area in the US.
If you're by yourself, you can get away with squeezing into a tiny apartment and making do (or getting roommates). If you're starting a family, this isn't an option.
I've started a family in Silicon Valley, and it is tough financially. We were lucky to find housing a below-market rent, and it's come with some hassles but overall it has been a godsend. Other expenses like health insurance really add up -- you should see the cost of preschools on the Peninsula. I like living here but it is expensive.
I would imagine that the cost of housing plays a large part in that. Housing in the Silicon Valley/Bay Area is insanely expensive. Maybe not as bad as downtown Manhattan, but still insane by the standards of pretty much every other metropolitan area in the US.
If you're by yourself, you can get away with squeezing into a tiny apartment and making do (or getting roommates). If you're starting a family, this isn't an option.