No way I would hunt without a sling. In the dark or just straight up traveling the firearm is strapped to my pack in rough terrain.
However, most the time I have the sling over my pack stays. If I just run my lumbar day pack I can't strap my gun to it. Sling over the shoulder or get into rough terrain or need both hands I can through it across my back with sling across my chest.
It never makes sense to me guy climbing steep, shitty, slippery terrain with a gun in one hand trying to balance. Just put a damn sling on and go. I have never had it get in the way or cause and issue. The one time I forgot to put my sling on I hated life...cut a piece of paracord and made one on the side of the mountain.