LA and SF seem trapped by their design. Sure they need way higher density, but that would require transit that handles density better than cars on a road. But in order to build high capacity transit they want people to prove that it would be fully utilized and that won't be true if you're servicing areas that are currently all single family homes.

So high density housing can't be build because there is no transit, and high capacity transit can't be built because there is no high density housing.