The problem is more than just OSR, for some reason there is an expectation that NPC do not cure about living, and would fight no matter what. Fleeing, surrendering, is what would happen if you want realistic fights. In most games I play (but no OSR) I ask for an *endurance* (whatever how it's called) roll when PC or NPC took enough injuries to be in the malus, it makes sense to fall unconscious at a point, let the PC take prisoner, and act as a safety breaker to not kill a PC stupidly as they're unconscious long before dying