“This one is thin and small, but it’s important. When you had something you wanted to tell someone, you would write it down on a piece of paper and paste this ‘stamp’ on it. Then they would deliver it for you, anywhere at all. But that was a long time ago …” The Memory Police by Yoko Ago.
For me, sending letters is just an excuse to send cute stamps. Many years back when I used to travel in Chinese trains, almost every third person was a stamp collector. The stamps may wonder why no one loves them anymore.