Warning shots are just for warning, seriously. How can you say they dont work? if someone is delaying, you hit em in the foot, then get the message, and continue, they step out of big cage while there, warning shot.
It is perfectly effective, and what it really lowers is people being killed for stupid little things. If we didnt have them, the ts would just all be shot when they do a little mistake, which makes the game a hell of a lot less fun as a t.