The Military is one of the few jobs in America that a person cannot legally just say "Fuck It!" and walk away from. Enlisted are bound by the terms of their enlistment and even officers, who technically can resign their commissions at any time, are obligated by the training they receive to serve specific periods of time following that training.
Because recruiters are what they are, people are often disappointed that service in the military is not what they were led to believe. It is also the truth to say, that many join the military as an act of desperation and after the crisis passes are unhappy with the life that they have obligated themselves to. This is not something that is unique to the American armed forces. It has been the case for as long as there have been soldiers and that is a very long time indeed.
Military service is hard. It is dangerous. The pay, especially for the lowest ranks, is meager. You spend long periods away from family and familiar surroundings, in rough company. You often find yourself living among populations that do not wish you well. The military enforces strict discipline to ensure that its personnel live up to the obligations of their enlistments. In the past, when time of war or national emergency made a large military necessary, a universal draft has been enacted. It was accepted that the enlistment of the individual was "for the duration". At least in theory, everybody was in the same jeopardy of having to serve and the service would be of the same duration.
The political power of the middle class in America has made a universal draft unacceptable. We now have an all volunteer military. The military has taken to arbitrarily extending the service obligations of active duty personnel. They have lowered the bar for the activation of reserve units to active duty in times of national emergency. This is foolish. Young people see their friends and siblings go off to the military, supposedly for a couple of years and then see how that quickly morphs into a decade. When they reach the age of eligibility to join the military, the best and brightest of them will quickly discard the idea, based on what they have observed.
The military leadership is poisoning a well it will need to return to again and again. This is short sighted and stupid. This is just another way they have sold out to Bush/Cheney and dishonored themselves. They will regret it, down the road.