Because the current overinflated housing market is a direct consequence (in the US) of loosening credit requirements for mortgages, the product of a herculean lobbying effort by investment banks in the late 70s to get the government to allow them to securitize mortgages (that is, immediately sell the off after origination), with the mortgage interest deduction (a subsidy to banks) the cherry on top.

Mortgages used to be boring and conservative, house prices were rational, but financial middlemen didn't make any money on it so it had to stop. It took the Reagan administration installing the Merrill Lynch CEO as head of Treasury to get it done.

The 2008 financial crisis and today's overinflated shitshow of a housing market are the direct result, along with tons of wealth creation for the rentier class.