Zoning. In Silicon Valley, there are restrictions on the number of units you can place on a site, and minimum requirements for parking, open space, etc. To put

Zoning. In Silicon Valley, there are restrictions on the number of units you can place on a site, and minimum requirements for parking, open space, etc. To put any meaningful number of units to house hundreds or thousands of employees would be impossible, or at least not economically feasible. And there are rules that separate commercial from residential areas.