The reason it would never happen is that, at least in the US, the government has been in the business of trying to make owning a house accessible to people who

The reason it would never happen is that, at least in the US, the government has been in the business of trying to make owning a house accessible to people who probably can't actually afford it. As much as people like to cast aspersions on "the banks" for the housing bubble, the government deserves a lot of blame as well for actively promoting the ideas that everyone should be able to own their own home. If they were to do what you propose, that would lead to some uncomfortable circumstances: the only people who can afford a home are the people who come from the middle class and up, which might not represent minorities in an appropriate way. And in such a case this does not bode well for politicians who are looking for votes.