While the FO3 system could definitely use a slight improvement, keep in mind that in most RPGs, HP, "Hit Points"
do not necessarily mean the amount of
physical damage: HP are supposed to be your ability to
COPE with threats.
Because, hey, we all now all the "health" in the world matters squat to a square bullet to the head, right? cause if it the system were that realistic, one or two bullets would leave you as a quivering mess on the ground.
So while you actually don't see it animated, it helps to think of HP decreasing while you're being shot to mean that you're dodging the bullets.

and when it's close to zero it means you're too tired to dodge any more.
Some RPG systems (such as the
http://en.wikipedia.org/wiki/Storytelling_System and I think
http://en.wikipedia.org/wiki/Gurps) and most CRPGs of late (
Dragon Age, FO3) have gone for a separate system to denote actual "injuries" or crippling. Nothing's near perfect, though, but they're improving.