There is/was a fairly straightforward explanation for the fiscal stimulation of home ownership and in the 60s government was not very coy about describing it: home ownership ties people into their respective communities by giving them a very tangible piece of "skin in the game". When you own a very expensive (relative to your total net worth) piece of real estate, that gives you a real incentive to take care of your local community. This in turn improves the stability of the society as a whole, since the large group of homeowners is not in favor of any real upheaval which might threaten the status quo.