In regards to bad S&C coaches, I think James Smith explained the issue best; he said: “due to the large talent pool in America, it’s much easier to recruit the best then to actually take the time to develop whoever you get.”
So really, the situation is were the management of American sports itself does not bring out the best in American Coaches (or Athletes). Now if coaches had to hang onto their athletes for 10 years+, it’s possible that would encourage coaches to think more of the development of the sport then personal gain.