As one U.S. Army veteran told me, he’s received more “thank you for your service” greetings in the last few years than he did in all the decades since he was drafted during the Vietnam War.

One card simply stated: “Thank You for Being My Person.” According to the Greeting Card Assn., Americans purchase around 6.5 billion cards each year.

According to organizer Jordyn Clark with I Got Your Six Ministry, about 200 cards have been collected, but her goal is to ...