Why Are There So Many Big Walls in Fantasy Novels?

https://themillions.com/2017/03/a-brief-review-of-walls-in-literature.html And: https://www.grmatthews.com/post/2017/01/07/walls-in-fantasy Thank you. This concept has been unsettling to me, and I needed some outside thoughts to clarify my opinion and thinking. And naturally, as a writer, I want to write about a BAW (big @$$ wall) in every one of my stories. Maybe it's a virus that needs inoculation?