In Ender's Game, promising children are taken to Battle School to be groomed as potential military leaders. The primary method of training is a team-based sport in zero-gravity. The kids train to fight effectively in this environment, mostly by using pistols.
But as we find out later, Ender is ultimately being trained to remotely coordinate fleets of starships light years-years away, and these ships already departed many years ago. While the game did teach leadership skills, why go through making it about physical combat? Why not just have them play EVE Online or something that is already a computer simulation, and devote time to developing leadership skills through that instead of physical combat?
That said, I really enjoyed reading about the zero gravity game and wouldn't want it removed from the book.