The electrical example is particularly interesting because it's generally legal to DIY things on a house that you simultaneously own and live in. Many (not sure if all) US states even have laws preventing insurance from forbidding such (although they can generally deny coverage after the fact if the incident can be shown to stem from your DIY work).

There also exist mixed zoning areas where you can run a business that hosts customers on site out of your house.

Presumably the big differences are incentives and scale. Scale wise, more building occupants justifies more regulation. In terms of incentives, there's probably less inclination to cut corners and be reckless with a structure that your entire family lives in.

I think I'm going to blame zoning on this one long before I take issue with electrician apprenticeships.