Not just subsidized mortgages. Also tax and other incentives, zoning laws that make it more difficult to build rental properties, and infrastructure that can't

Not just subsidized mortgages. Also tax and other incentives, zoning laws that make it more difficult to build rental properties, and infrastructure that can't support (or is specifically designed to prevent) the kind of population density it takes for building rental properties make financial sense for developers in many areas. Combined with a lot of political tailwind behind these kinds of broad-spectrum public subsidies of landowners, because in the USA it's common for working class folks to think of themselves as really just being rich people who happen to not have a whole lot of money.