What if they believe in the cause and are ready to fight. Many are, I assume. Many not also of course. Look at Pat Tillman... and many others.
It's not on me to judge them. This will be done by others after this material experience. Sure there are a lot of them out there but i think most of them just want to go home to their families, see their kids grow up, spend holidays in foreign countries and do a job they love and don't want to see the dead bodys on the battlefields.