It's also important to consider what the code is, anywho decides it, and for what reasons.

Most cities adopt a mishmash, but they take them from large private organizations that publish big books of code, and how that whole process happens is far more opaque than most standards bodies because it's so obscure. Is there evidence backing the changes? Is it vibes? Is there financial benefit for the code writers for certain choices?

This mishmash of choices by local cities also greatly reduces building efficiency, because even if I learn the fine details of my city, that doesn't guarantee I can apply my hard won code knowledge a few miles away.

Building code is important and I wouldn't go as far as saying "if you own the house you don't have to follow anything" but our current situation is also not providing much safety in the US. Code mostly exists to justify checks, not improve safety. A simpler, more uniform code, with clearer motivations and evidence would go a long way to reducing unnecessary costs.