It's not just the markings, it's training for the crew since being a gunship vs being unarmed is different, different equipment inside for the litter vs door guns, less medical equipment because you need to have ammo, different crew since a gunner isn't a medic, etc

That was my thought as well. If you're a boxer, you have rules that you must follow. In a match you don't need to worry about getting hit below the belt. If you ended up in a street fight however, you can't make that same assumption.