In theory, building inspections at each stage of construction should find omissions and other non conformance while it's economic to fix them. I do acknowledge that building inspections have a lot of issues, one of which is different inspector, different rules, and a later stage inspector may have you redo something the earlier stage inspector said was fine (sometimes, even with the same inspector!), but the idea is there. I've heard that locally, a lot of inspections are done by video conference now, and contractors find that goes a lot faster and more direct. Not sure if that'll stay post-covid.

It's also difficult to know what's on the inside of built houses (which is why inspection is supposed to happy during construction, not after). Commercial buildings often have both plans and as-built drawings; but residential buildings don't, and when you get on-site and the plan doesn't match the house, you really don't know what's in the walls. Some sort of government driven new code compliance inspection for existing housing stock seems really expensive. Even public use buildings take a long time to get code compliance updates, such as retrofits on unreinforced masonry buildings in many places, and there's both more risk and more enforcement power for public use buildings.