"Which sums up what all servicemen believe, else they could not serve."

In the US many young, socio-economically poor, mostly people of color, end up joining the military because they have few if any other options available to them. Military recruiters prey like hawks. Governmental so-called education legislation ("No Child Left Behind") mandates that schools hand over contact information about students to the military for recruitment purposes. Wealthier and whiter parents know how to opt out of this. Military recruiters tell lies upon lies to get enlistees, often things like, "If you enlist, you won't have to go to Iraq."

Patriotism might have something to do with it sometimes.