POW/MIA flags at Interstate rest stops - why?

The Subject: line is the question.

Driving across the United States, I noticed that most Interstate rest stops – not truck stops, but state-operated rest areas – fly the POW/MIA flag. Why? Is the POW/MIA flag in any way official? Why its near-universal presence at rest stops?

It is not official, and it is not required by any law or anything. Frequently, veterans fly it just to show rememberance to those who are still missing.

It’s more of an unofficial flag that gets flown alongside the national and state flags. A symbol of patriotism.

Just a way of saying “Thank you”. That’s all . . .

Unfortunately, I don’t have one, but I have my POW bracelet.