my apologies. I should have used the qualifier "for civilians".
Are these manufacturers wasting their resources by combining a 16" barrel with a .308 round?
No, they are not. They are selling them because people buy them. They are excellent combat type weapons that can deliver a bullet through walls and doors. However. most people here are not looking to shoot insurgents popping up from behind mud walls like our troops did in Iraq or A'stan.
The 308ARs make excellent pig rifles because of the penetration and the fact that you have more targets of opportunity. My rifle has a 20 inch barrel, that's were the extra 4 inches of barrel help.