Actually, there is the term "civil service" that denote all other government jobs that are nonmilitary. I always referred to my mother as a civil servant (she held a government job for 35 years before retiring)

My husband is a career sailor, in his 3rd enlistment, Iraq war veteran, and he takes more of a "it's a job" look at it. He still doesn't really know how to respond to strangers' "thank you for your service" even after 14 years.

I think people say it because they respect someone's willingness to risk their life. Especially since we are taught that the military defends our freedom.