A premade map means the game can be a lot shorter, and the "Don't break blocks" doesn't mean people can't get blocks from creepers blowing up. The reasoning behind is to discourage mining, which can take a while. The Yogscast recently played a team Hunger Games, and the map for that was pretty good, and whoever the organiser is can randomise what is in the chests, so no scouting.
And seconding the invisible+fly thing, I would like to watch the events, not take part. And the spawning thing can get out of hand.
