Demand isn't just about need, it's also about quantity. If there are a million households who need a housing unit,
need it so they're not on the street, but there are five million housing units in the area, housing will still be very cheap. Because 80% of the units will be empty even after everybody has one, and people are not going to pay anywhere near as much for a second one because they don't need it as much.
Whereas if there are a million households who need a housing unit and there are only 750,000 housing units, you've got a big problem. For which the solution is to build more units.