This is an important point, so much of the so-called diversity problem with Silicon Valley is driven by the enforced colocation of techies into a small geographical area in central CA. You also lose out on people that are more family oriented and not apt to move far from where they grew up. There's plenty of smart and talented people that are hard workers who need that kind of proximity to their loved ones and they can't just pack up their whole extended family and move to SV.