So, why did America adopt its decades-old exclusionary zoning policies and culture? Blame the central governments of the 1920s:
The leap from morality to legalism was solidified by the Euclid Supreme Court decision of 1926, which confirmed cities’ right to segregate land uses. Around that time, the American Planning Association encouraged cities to adopt zoning codes that would promote, “health, safety, morals, convenience, prosperity and the general welfare.” In other words, they had carte blanche to be as exclusive, racist, and elitist as they wanted. But whereas racism and elitism would not hold water publicly, planners came up with economic and political justifications for strict separation of uses.
And it’s not just to bolster ownership:
The United States does not have an “ownership society” so much as it has a sprawl society. The United States ranks 17th out of a survey of 26 developed countries in homeownership rates, so homeownership per se does not explain why European cities are compact and American cities are spread out. The difference lies is in whether those homes share walls with other homes. …
Zoning was originally conceived as a way of separating noxious or harmful land uses from people who might be harmed by them. Europeans enacted hierarchical zoning, in which objectionable uses were excluded and anything not explicitly excluded was permitted.
The United States takes the opposite approach. Noxious uses aren’t segregated. Instead, prized uses are the ones that are segregated. Under this “flat” zoning scheme, “urban and suburban worlds in which everything was not only in its place but was also in its own separate place.”