Good comments, JohnKSa.
Most defense-type firearms instructors can tell you that they often see people who are good, self-taught marksmen, but whose gunhandling/safety skills suck.
You see guys who can hit a gnat's eyeball at 25 yards, but who cannot for the life of them clear a double-feed in less than 10 minutes. Why should they be able to? On the range, there's always plenty of time.
You see similarly excellent shots who can't seem to keep track of their muzzle direction.
Good instructors don't allow students to sweep other people even while learning, of course. But you can tell when a student has no idea where the muzzle is pointed and when they are about to sweep someone else if you don't stop them. So that's when you step in and catch the guy's attention. Again. For the 14th time that day, you suggest that he should not just allow his gun hand to drop to his side after firing, but should instead deliberately keep track of the muzzle at all times while the gun is in his hand. And then you watch him do it again after the next string, because he's literally had years of doing things that way, and only a couple of hours of being told to pay attention. You cannot undo years of mis-training in a couple of hours, no matter how hard you try.
The thing that really amazes me is that these guys often show up in a class not because they really think they need to learn anything, but because it'll be a fun vacation, or because they wanted to take their wife/adult son/best buddy to a class with them (so the other person would learn to shoot), or because they just want to have better looking targets. They don't come to class to learn everything we teach, just to improve their marksmanship skills. And marksmanship is the one thing they've already got down pretty well!
These guys often don't know they need to learn safe gunhandling; after all, they've never shot themselves so they're already safe shooters -- aren't they? And even if they carry regularly, they don't know they need to learn to quickly and decisively manipulate a gun, clear malfunctions quickly, or draw smoothly, because they figure pulling the trigger is all the gun-handling skill they'll need. They don't need that high-speed, low-drag stuff. They've got high quality guns, so they'll never have a jam under pressure. And they they they won't need to know how to draw safely and smoothly, first because they think they are already safe (even though they aren't) and second because they don't think they need to be the fastest gun in the west (they don't -- but smooth is not only fast, it's also safe. Fumbly is not only slow -- it's unsafe...)
</rant off>
pax