Another possible reason for bad workmanship in new builds, and I'm sad to say I had a lot of experience of new builds during my House Bashing days, during the building booms of the early 70s, was the use of Labour, possibly 1 skilled Electrician as a lead person with 4 or 5 "Apprentices in the later stages of their tenure as Apprentices".
This would have been all they had ever done, and had in most cases never been offered the chance of doing any Commercial or Industrial type work, solely because the Management found their usefulness on housing developments far to useful to give them any other sort of work experience.
I ran a site like this, on one occasion, I had a Mortgage and a family to feed and clothe, so my concern was their welfare not the Lads on site.
Many of them thought that House bashing was the B all and end all electrical work, and either stuck at it or decided to go it alone and work for themselves, taking the skills, or lack of, with them, to fester on in infinitude.
I'm sure there will be many of us who recognize this sort of thing, it's therefore not surprising we have the sad state of affairs that our trade is in today, bung a few cables in a new build, give up College and carry on with the basic qualifications and the only experience will be housing work.
And most of that work will be priced so low that there will be little or no scope for work ethics, and pride in their work,