It's an abstraction. A bullet hits someone in the head and they die. It doesn't cause points of damage. The abstraction makes sense, since it's an RPG and not an FPS. You're constantly reminded that you're playing the a game, since it's all isometric. The player is encouraged to imagine what's really going on in his head. Did the bullet enter the player's brain just because it his his head? Or did it merely graze him, since it wasn't a fatal wound? Maybe the leather jacket helped the player get lucky with something in its pocket. Maybe he was grazed on his shoulder and the leather altered the course of the bullet. That's up to you to decide, since you can't actually see it and at most have a text prompt.
The goal of first-person perspective and real-time combat is to put players into the game, and try to make them forget they're playing the game (to some degree, not fully, obviously). This is why Bethesda's combat will always be lackluster. Because they're mixing RPG elements that are abstractions with the opposite design philosophy of FPS games. You constantly see the bullets hitting your target in the head, yet they don't necessarily die, depending on stats. You constantly see the bullets hitting their space suit, yet they don't suffocate.
This isn't just a Bethesda problem either, but again, they're the ones who decided to make space suits into cheap, FO3-style power armor. That wasn't necessary, and it makes the problem worse.