Is because its so easily countered. nogive and done. Again, why are you being such a hater on the tactic when the solution is a toggling command that has no lag that can be turned on and off at any time? Are you equally a hater of people following you when you don't want them to? (nofollow). Or people rescuing you when you don't want them to? (norescue) Or people looting corpses that you created (corpseguard on/off).

Really, come on.