Walls in Children's Books and Shows

Here is the question. Have you ever, in real life, seen a brick or concrete wall standing in the middle of a field? I know I haven't. Yet they are a really common feature in kids' books and tv shows. On old school sesamie street they were a common setting. Everything interesting happened over the ledge of a waist height brick wall. In Hop on Pop, many tall and small people play ball on a wall and then, inexplicably, fall off of said wall. Charlie Brown and Linus' classic place to talk is while leaning on an elbow height wall. Where do these walls come from? What are there purposes? Do they exist in the United States? Is Canada just behind in its field decorating decor? What's with all the extraneous walls?