If you don't, you cant be revived. this to stop kill spawn revives, one of the most exhausting bullshit things in this game.
i agree with sgt security, we need a rev lock! (doesn't mean i disagree on the others, but his solution fits better in the game and won't touch newbies that otherwise would be doomed and cause unnecessary chat rage ;-) but also a message that someone has locked rev! - or just a command that cause force respawn! - maybe with a 5s move penalty or that removes the body from map ;-)
There is already the force_kill command that used to be bound somewhere. This will kill you and disable reviving.