I mean the houses are "designed" insofar as plans are drawn up, etc. They're just all the "same" and the builders want the ability to "add uncharges" so you have a basic house that looks pretty decent, but once you select all the available admins (the three car garage, dormers on every root, gables everywhere) you end up with a McMansion.
The fact is that we literally do not design homes in the US; over 90% of homes were just built by someone. That someone does not stop to consider design, aesthetics, ergonomics or joy. House developers are more or less doing enterprise sales. They just go by a checklist and the developer with the most checks wins. "Upgrades" merely change the quality of the thing on the checklist (formica -> granite), but thats the extent of it.
1. https://www.moma.org/calendar/exhibitions/1714 2. https://en.wikipedia.org/wiki/Kaufmann_Desert_House 3. https://en.wikipedia.org/wiki/Stahl_House