1) As others pointed out, need to account for seismic activity. 2) The invention of air conditioning (and low prices for heating) allow inefficient architectur

1) As others pointed out, need to account for seismic activity. 2) The invention of air conditioning (and low prices for heating) allow inefficient architectures while maintaining reasonable comfort. 3) Corporatization of construction led to structures that are efficient and quick to erect. 4) Insurability of a tract house with standard architecture is much better, due to predictable materials + labor costs.