For many years now I have used nothing more than the GI web sling, I prefer the ' cotton ' over the nylon versions as they dont tend to slip, the 1907 leather when applied correctly is a great alternative and i have at least 2 on some way old military match rifles i still use. The larger point here I believe, is that scores will improve, and lethality is more certain when utilizing an aid....sling. If you desire to use bipods tripods or nothing at all is certainly your deal, but from the thousands of students I interacted with during my time as a Senior instructor with not only Appleseed, but 4H shooting sports i can attest to my claim.
I believe that exposure, or lack of, and relying on benches, bags and such other items has engineered a decline in the use of slings as their are other, abettedy heavier/ bulky things that are trendy and of some use for those who dont care for or are uninitiated with the simple sling.
I'm not trying to criticize or critiquing anyone for their personal views here. I dont use benches, bags or bipods. I prefer sling supported shooting positions and have for a long time. But that's me.