They built it somewhere someone lived and owned the land, they do not built a town in England of high density in a field that no one has occupied for generations, connected to new roads that didnt exist before.

Yes as we add density we do add some items like extra schools, sure, as the population is growing.

No one is going to build a town of 100,000 off a new non-existent highway they also built somewhere in CA. It's going to go somewhere that has some density already (and has that density usually as it is near something desirable).

They also dont built is near where THE sfhs are (as in all), they built it near SOME of it. Thus the NIMBY desire for it to fall somewhere else. We cant make ALL the sprawl dense, we don't have the people for it. If the Bay Area counties had pop density of urban areas of East Bay across all of it, it would fit every CA resident with none left to populate LA, San Diego, Sacramento etc (not a recommendation, just a note that density can't be everywhere).