Our vision is circular and not rectangular. Circle is the normal shape because your eyes are circle. Your field of view is circle. The normal shape for photography is circle. In the beginning it was a small hole, later a circle lens. Every image in your eyes and photography are circles.
I know next-to-nothing about photography, Sam...but I'm having some difficulty with some of your suppositions. Nothing about my vision seems circular. I am blessed to have a full-field of vision. I get no sense that my vision involves a circular shape at all. And most photographic images I've seen are rectangular. Unless, of course, I'm totally misunderstanding you--which is entirely possible.