Why is it weird to some people? If I'm on a park bench, chilling and enjoying a beautiful day... why would I not people watch? It's not like I'm stalking and taking notes and shyt. The act of observation is crucial to me. The different idiosyncrasies and reactions you notice that you may not have before. Its interesting shyt to me.
Plus it's fun to make up stories about people you have no idea about. Like some Wonder Boys shyt.