I served in the Navy for seven years, 3 of which were in Weapons Department, and a year of that in Air Ordnance. The Armory was on the other side of my office wall and a 500 yard range was across the street. I shot something every day; shotgun with clays, M1, BAR, .22s, Thompsons, "Grease" guns, .45s, and 38s (the pilots survival gun at the time), plus my own personal weapons. I shot more than any ten Marines going through Boot Camp.
I believe the military adopted the small caliber for logistics reasons. They could move and carry more ammo than the .308 or .30-06, plus the lower cost. In addition, a wounded man takes at least 3 enemy out of battle, while a dead man takes out only one. Were I in a combat situation, I'd want a .308. (Getting it would be a diffferent story.)
I don't allow "deer hunters" to use .22 cal. rifles on my property, and here's why. Most of them buy a rifle, sight it in at 100 yards, and it stands in a closet 363 days a year. A box of ammo lasts them 20 years. They drag it out one weekend a year so they can put on their orange hat, go to camp, and drink and play poker with the boys. The odds are they never get to make a shot, and if they luck out, it is usually misplaced. They are not riflemen or hunters. In the first few years I owned this farm I spent more nights than I care to remember walking around the woods with a flashlight looking for blood. The larger calibers leave an exit wound, hence more blood. I have a handful of friends that I allow to use anything they want because they are riflemen, experienced and ethical hunters. Most of the folks on these forums fit in that category simply because if they didn't, they wouldn't take the time to be here.
Pete