Divining motivations for VOLUNTEERING is a fools errand. Some do it because they're choice is that or a prison sentence. Some do it for adventure or out of boredom. Some do it because they want to go kill some "gooks","rag heads", or whatever the picked enemy of the day is. No doubt some do it because they believe that it's patriotic.  But one doesn't define a patriot by fighting or not fighting, by voluteering or not volunteering. From the Websters:
"one who loves his or her country and supports its authority and interests"

Drafted or volunteer, doesn't matter one iota.