SOF can go lightweight for many missions. When you go out hard and fast -- and come back fast you can use the lightweight stuff; it'll tear up but you can replace it easily back at base. With your American Infantryman; he's out fro weeks at a time -- if it tears, he's out of luck. Yes, in an Afghanistan or Iraq like situation, it can be easily replaced. Every war is not like these two and every replacement pack or harness displaces food and ammo...

Good examples are the Mk 46 and Mk 48 Machine guns; great for SOF -- bad juju for the Infantry; they aren't tough enough; lack of durability kills...