A tourniquet is a machine you use once
It sits in a pouch for years, in heat and cold and sweat, and then it has one job on the worst day of someone's life. It gets applied by whoever is nearest — often with one hand, often their own leg, always with adrenaline in the way.
Almost everything that makes a tourniquet fail is decided long before that moment: the plastic that goes brittle, the windlass that flexes, the strap that slips through a buckle when it is wet. Those are manufacturing decisions, not user error.
