I would imagine speed/cost/aesthetics. The builders aren't going to think about long term repairability and few home owners would know to think about something like this or come up with a workable (and code compliant) solution.

We have had to be extremely diligent with our contractors because of the number of times/things they do where they just operate on the autopilot of what is typically done. Its human nature, but the norms in building homes to me are just wildly outdated. Wildly.