hitpoints are necessary, otherwise you spread yourself... cause you would have to calculate potential limb cutting, and what happends then? you need to calculate bleeding, and how do you restore a broken arm? you need an hospital and magic to regrow your arms... otherwise, you'd be a plastic doll with everliving arms but that can yet hurt independently from the body. I prefer to see it the way it is right now, really.
EDIT : with 0.700 however (fixed in 0.701) it was unecessary to debate. 1 arrow would probably do instant kill on you even if it was kilometers away... damn archers in 0.700, they made me feel like **** EVEN witha shield, but that' sout fo topic...