either as a reward, something for the troops to do when they get bored(even though if they want to play cod4 they could probably do it in real life. lol), or so assess the proccessors and computing powers to see how they can be used. that or maybe the joint chief of staff and higher ranking offcers want to see how good they are at war games. maybe theyll buy 300 xbox 360's to "assess" halo 3 and gears of war.