This is because code approved, correct piers or footings were not poured, the load bearing points were not correctly stacked on each other, and the correct hangers and brackets were not used in the appropriate locations.

This is because they were nailed from the outside, not shimmed correctly, and the builder did not take the time to check for plumb, level, and square, with the appropriate reveal requirements.

This is because the installer is not using the correct clamps and doing these micro adjustments as they install. Then there is a whole day or two of doing hardware and adjustments after the installation is finished. Some are just throwing the handles and hinges on and getting paid. As long as they open and shut.

This is because someone didn't glue, pin nail them, or cut them correctly and just decided to caulk over it.