The last months there was again a case of a building constructor using less structural elements than it was legally required to, also violating the number specified in the blueprintS.
If buying and moving homes were a more frequent event, buyers would play more "rounds" of this game and eventually become wiser to the ground rules of it. Reputation would start to matter, and developers, contractors, et al., would need to work harder to ensure they didn't get dinged. As it now stands, except in the luxury market, really, where people custom build homes, no one cares about a developer or contractor's reputation. So they don't have any reputational risk on the line. So they happily cut corners wherever they can get away with it.
(And I'm willing to bet that even the luxury/custom buyer barely has a clue when it comes to evaluating the quality of construction and materials.)
Nope, that's exactly it - it's cheaper and faster for the builder to frame a house small and simply. They've found that people spend money for houses based on location, size, and the visible stuff (like nice paint jobs and shiny appliances). They could spend twice as long as 40% more in materials and the home would sell for 2% more - not worth their time.