I always make players sign a signature at the bottom of every CS with their own username. In doing so they agree to allow their characters to be killed by me in any way I see fit at any time which I decide. In exchange it's generally agreed (though not formally) that if I do kill them, it's for good reason, not random chance.

That is, level risk and reward. If someone attempts to dash for a better position they might get hit but that doesn't gaurantee a kill, being wounded can still result in some pretty awesome character development.

As for quartering off death entirely... That completely eliminates an entire level of storytelling. Why? Because someone is apparently unaware that if their character [i]"dies"[/i] they can literally remake the exact same character in a different role play. It's not like I hold the copywrite to your character or something, so just like how in comic books people keep getting remade and reincarnated a hundred times, there's absolutely no reason you can't hit the redo button on a character who died. Who knows, maybe there was some critical flaw in the design. For instance: Being so brazen and brave, that they walked straight into the kill zone of a machine gun nest and got shredded to bits. Well, now you know in their next iteration to tone down the brazenness a little, make them use cover more, work with allies to approach the nest from multiple angles or to get them to provide covering fire while you move for that next piece of cover so you can chuck a grenade inside.

The only "valid" reason for not allowing the death of a character (aside of course from godmoding by other players or other such unreasonable situations) is emotional attachments. That one cannot deal with the idea that their character can, well, you know... Die. And not just die, mind you, but probably fail at whatever overarching goal or task they had. That's not easy for some people to deal with, I find it's more common the younger a person is and the more privileged a person's youth was--that is, how exposed they were to the concept of [i]death[/i] and its permanence.

tl;dr: Death is to storytelling what meat is to diets. You can live without it, but you miss out on a hell of a lot of good tastes and easy to access meaningful things.