Many of these "volunteers" are doing it for the college money but then finding they can't go to college because they're being sent for 4 or 5 tours in which it becomes painfully obvious that they aren't fighting for freedom but rather acting as mercenaries and pawns for the military industrial complex. Couple that with inadequate mental care for sufferers of PTSD and lack of deprogramming once reintegrated into society and it's pretty obvious why so many are choosing to take the easy way out.