It seems like one of those cascading series of perverse incentives up and down the value chain. The subcontractors want to cut corners with the contractor. The contractor wants to cut corners with the developer. The developer wants to cut corners on the project in general, passing the headache onto the buyer at some point after the eventual sale. Almost no one in this mess has incentives aligned with doing things correctly.

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.)