It's a bit of a weakness of hitpoint systems. A common response is to view HP as representing fatigue and minor injuries that gradually weaken a character until, at zero hp, they finally take a truly dangerous injury. In practice, I've never seen a player or GM resist the temptation to describe attacks that reduce HP as causing serious trauma to the flesh. Still, HP is a feature of most older d100 horror games, so it needs to be a feature for maximum ease of compatibility.
I am working on a more modern horror system that will not use HP at all.