I would wager that it's because there are folks who applaud the private sector for stepping in on a big problem. I would argue it's a general positive when we don't have to rely on government to solve all of our problems.
Because nobody is being forced to fund it, as is the case with the state. And the state would staff the administration of the new construction with pensioned state bureaucrats, whose pensions are already bankrupting California. Unfunded state liabilities from pensions are somewhere between 333 billion and 1 trillion, depending on who you ask.
And then once constructed, there would be forces wholly removed from the natural demands of the population, as represented immediately by the encompassing markets, determining how the housing is to evolve over time.
People should be much more reserved than they are in terms of handing things over to the state, there is much to be lost.