The last time I was thanked for my service it was a mom who brought over her 4 year old son. They said "Thank you" and I gave my standard reply: "You're welcome." I then commented on the little boy's shirt because it had F-15s and F-16s on it. It was genuine.
I think that our fellow citizens are doing the best that they can. To say "completely disinterested" is a bit unfair. How do citizens hold politicians accountable? Elections. Over the last few years our fellow citizens have delivered us several different configurations of government between Democrats and Republicans: President, control of the House/Senate. Nothing really seems to change. In fact, last I heard, we're thinking about sending more troops to AFG for the sweet train, advise, assist goodness.