Well, think whether the market conditions that lead to it could be recreated today, and then you'll see how the free market fails to deliver a lot of housing fast. Developers have long ago realized it's better for them to pump out fewer houses with more profit margin slower, than lots of houses with little profit margins. They get a planning permission on a giant site for a 1000 houses but only build 50 a year to not disrupt the high prices they can charge for each unit. That's free market for you right now.