Rich Tech entrepreneurs, executives, highly paid programmers, and VCs want to live close to the tech "factory" and they want it to be a nice place. They don't care where everyone else who works there lives, just as long as they don't screw up their nice neighborhood with excess traffic, pollution and density.
It's as simple as that. All this stuff about economic policy and zoning laws and the general decline of western civilization is a whole lot of overanalyzing, IMHO.