Has more to do with availability of employment than patriotism I am sad to say. A kid out of high school can at best get a job at McDonalds if they are lucky. As small as it is a military paycheck is better than they could expect elsewhere. Also, many are raised by poor parents and are pushed out the door come graduation.
Small? I’m guessing you haven’t seen a pay scale for awhile:
http://www.navycs.com/charts/2014-military-pay-chart.html