I doubt there are many on this board that shoot poorly in a controlled situation. When you are in a hunting situation and the buck fever is kicking in, you may be puffing from exertion, have no steady rest, and maybe time is very limited, yes maybe.
All the more reason to take on a target area with higher percentage of sucess.
Yes anyone can shoot poorly. I' ve seen that happen many times.
I once stood next to a fellow who emptied his magazine at a spiker standing broadside at 50 yards, not one shot connected. I took the animal for him with a well placed single shot, then made him test fire his rifle. He produced a very tight group, so nothing wrong with the rifle.
Yes headshots save some meat. Just yesterday I shot two sheep (About 150 pounds each.) with headshots, but in a very controlled situation. These were for the pot, shot in the paddock, on the farm, at 50 yards and with a nice steady rest (On the tractor tyre.) I had all the time in the world, and yes the shots were effective.
As I write the roast is wafting from the kitchen..mmmmm..
Earlier in the week I was hunting Chamois and faced with a similar shot over same distance, plenty of time, good rest etc. But choose to take a well placed heart shot, which was also very effective. Result a nice fat buck for the freezer.
In a hunting situation, I personally do not have the confidence that I can take the low percentage shot accurately in most scenarios, and would rather sacrifice a little of the meat.
How much meat would you loose from shot damage, I' d say 2-5 pounds at most, although at times the bruising is extensive and can ruin a whole quarter or more.