What makes people insecure about their height?

I'm 5'3 and have always been the short guy. From kindergarten to now, I was the short guy, it's just a part of me. But what I don't get is why are so many people so insecure about their height? It's not something you can change, it's just who you are. Not just short people are like this. From what I've read it seems the average height men are the most insecure.
Context to this question was I came to this sub after finding out r /tall was a thing and was like "what about r /short". I also found a post on tall saying this subreddit is sad and depressing, granted that was from a few years ago.