It doesn't happen as much in plumbing or painting because these fields have not had rapid change in the last few decades, so common practices have stabilized. P

It doesn't happen as much in plumbing or painting because these fields have not had rapid change in the last few decades, so common practices have stabilized. Plumbing also has standardized code and inspections which pretty much make sure that everyone is doing the same thing the same way. And still there are differences in quality. Look at what two painters will do to a piece of shitty material like an oil-painted unprimed piece of plywood. One will sand it down to the wood and prime, the other will just slap a coat on top, and you'll have flaking in a few months.