About 20 yrs. ago I built my first house, and put the plumbing out for bid with a full set of plans to three firms. The lowest bidder had worked for the framing contractor on several jobs, so we went with him. He ran the sewer lines, then said to let him know when the first floor framing was done, so we did. He arrived on the job and said, "S***, why didn't you tell me the gas pipes needed to go under the slab? Now I have to run the gas pipes in the framing." And it was a ***** of a job, with lots of corners, doorways to go over, stairwells to avoid, etc. I said to him, that is why I gave you a set of plans...
And boy did he ever get even. The copper hot water recirc lines started leaking from pinhole leaks inside the wall 3 yrs after we moved in due to using the cheapest thinnest tubing available; the downstairs toilet flange was mislocated, so he put in an adapter to move it over 6 inches that does nothing but clog; the upstairs shower valve had hot and cold reversed; he used 1/2" tubing for the hot and cold supply lines to the Jacuzzi tub, so it takes 30 mins. to fill; then he took off to go fishing in Alaska before the finish plumbing even started.