It seems doctrine might be skewing the direction of things or thinking here.
Most of what Im referring to when I think of its use, is basically a replacement for a shotgun loaded with buck, and where and why you would use that. The advantage being, you dont have to carry the rifle/SMG "and" a shotgun, you have both in your hands with the select fire gun, and move back and forth with uses, with a simple "switch" or use of the trigger, depending on the gun.
Close up, in or around buildings, tight spaces, etc. Its a much handier gun thats basically just point and click. Put the front of the gun on the target and give it a quick, short burst. Its not suppressive fire, or how many seem to think FA fire is used, its a quick, deliberate, short burst (or more if needed) on target.
Aiming isnt aiming in the traditional sense, and more along the lines of Applegate point shooting, where you shoot over the top of the gun. You use the stock and normally shoulder the gun with a good solid mount, as you would when using the sights, and you are aiming, but not with a traditional sight picture using the sights. Trying to do that is about worthless and impossible, as you wont maintain any kind of sight picture and just get lost in the sights trying to do that. Shooting over top of the gun/sights works well and is very effective. Of course, this is at the close distances Im talking about. If you need to shoot further, its "aimed" fire in semi, as it should be.
Im looking at this as a multipurpose individual arm that covers more than just what a semi gun would. And most of the time, if it had a selector, it would be used in semi, and if it didnt (this applies more to older open bolt guns), trigger control on most of the better guns, will easily allow you to squeeze off well aimed single shots.
This is why I was asking about training above. I understand that the military has a lot to deal with, different MOS's, training and ammo costs, etc, and Im sure its just easier to do what they do. And maybe the returns arent worth the effort too. I just think a lot of the attitudes are based on a lack of understanding and what can be easily attained, with good technique and a little hands-on training, and at least I see the advantage to that.
Then again, with the prevalence of armor, and the trend away from pistol caliber guns, it may all be a moot point. Not that things like the M4's cant be used, they certainly can, and woudnt be any trouble, buy they still arent as handy as something like a MP5, M45 KG, Beretta M12, etc., which I think would be perfect for civilian use, as pretty much anyone can easily shoot them.
But who wants to pony up $35K for a transferable MP5 these days? It really sucks to be living in 2021. Surplus M1 Thompsons back in the 70's were $70, M3's even cheaper, and ammo was dirt cheap.