Government can apply prop 13 style 'minimum payments' along with the deferred payment. Or make people do reverse mortgages and make the market sort it out.

Usually although, you have provide some sort of incentive to people adopt something, and no taxes vs some small amount taxes is attractive to a voting block. And democracy is getting enough voting blocks to get you over the pass rate.

Also since government works over large numbers and is very long term, they can do actuarial calculations to see when revenue would kick in and issue fairly reliable bonds based on it.