Maybe substance abuse but my observation is the attitude: Throw it together, forget quality, and get on to the next job so we can make more $$$$$. I was at jobsites at all stages of building and, again, never saw any carpenter use a square. Never even saw one at a jobsite.
Quality: I was told of a local builder who was found to staple cardboard to the walls. He had run a string along the wall and was stapling cardboard in the low places. When asked why, he stated that this would make the sheet rock straight where the backsplash of the countertops would be and prevent big gaps between the wall and backsplash. That impressed me!
A diamond is how coal reacts under pressure.