Isn't everyone who works for the government somehow serving the public? I'll make sure I thank my local DMV clerk for doing their "tour of duty" next time I'm there.
The tour of duty metaphor isn't perfect, but I've always interpreted the "tour" part to refer to the term limit. Everyone in the DS and at 18F has a hard term limit. Can't speak for every municipal government, so don't know about your DMV, but most federal employees can keep their jobs beyond four years if they choose to.
I would bet that a DMV employee would appreciate a thank you, though.
