> People move here because they like yards and redwood trees and vineyards and hiking trail

no, they want jobs. you can get outdoors anywhere in the US, but only a few places in the US actually have a super vibrant economy.

and NOTHING precludes turning SF into a stack of 120-story high-density towers apartments for all family types and leaving the redwoods and grassy fields alone.

nothing but the unwillingness to go density, thus ensuring the grassy fields will slowly be turned into cookie cutter suburbs