In the mid-century era from World War II (or even before that) to around 1990, America had a mass market common consumer culture. With the fragmentation of that culture accelerating post-1990s, the upper middle class and middle class began to develop distinct cultures and folkways. Even removing race and politics as factors of division would not address this, because even among whites, the upper middle class and middle class now have different and incompatible definitions of the good life. This creates local political dissension and perverse incentives in areas like land use.
