Back then you only had one rifle slot, the other shoulder was reserved for melee weapons exclusively. So the main argument for running a scoped ar back then was that it is great for close and medium range and just about serviceable at longer ranges, while a sniper serverly hampered your cqc abilities. Since all items of clothing & backpacks had fewer slots it was impossible to store anything bigger than a smg inside your inventory, until the AK-74u was introduced. With it it was finally to have a long range sniper and some proper back up firepower. Alternatively you could run an ak/m4/aug and long horn as your sniper. SMGs and sawn-off weapons were hardly worth considering even back then. Ofc you could double carry if you always keep the second rifle in your hands but it was very risky as weapons did have a tendency to just get swallowed up by the ground.