I have 2 sashes, one green, mushroom and dark brown to go with my Gov issue night camo smock and the other white and off white to go with my winter white camo. As a sniper they blend in better in those 2 environments [limited visibility and snow] than exterior equipment, they make next to no noise and are far more comfortable than any kind of equipment belt. When I wear the night camo smock in town - running errands etc - the sash is very comfortable holding the smock snug around my body. I often wear the night smock casually about town in the winter because I have an insulated liner for it; the sash keeps cold wind from coming up onto the small of my back.
I have just ordered a third sash in off white and mushroom to go with my new US M1916 Officer’s Mackinaw [available at What Price Glory] as I often recreationally ride horses not just in the other 3 seasons but in the winter too. And for the same reason, keeping the cold from coming up under the bottom of the mackinaw.
In extemis you can easily make a tourniquet or sling out of the sash - far more easily than with a belt. You can also hold a battle dressing tightly in place with it.
It’s a very handy piece of kit.