A big part of the problem is the same with cars; nobody makes used cars, and nobody builds used houses. The buyers are the ones with money and they drive the demand.

https://www.amazon.com/Building-Affordable-House-Fernando-Pa...

(Some of the obvious wins have taken over quite quickly; almost no builders frame roof trusses anymore and instead bring them in from a factory on trucks and crane them into position - three men can do in a day what would have taken an entire team a week.)