There is no prefabricated site-work. A house needs foundations, underground utilities, pavements, and landscaping.
If tires had to be manufactured at the car-buyer's home or place of business, cars and buildings would be more analogous.
The premise of the article is that home building is economically inefficient. As a mature industry in a capitalist economy, that requires supporting evidence. That so many people cannot afford market rate homes in desirable locations is not evidence that a free-market profit driven economy isn't working.
Mortgages are the important product produced by the home-building industry. Below market rate housing is by definition not going to be willingly sought by free market actors.
