The spatial Finder treated files and folders like physical objects. There was only one window on the screen for a given folder because a physical folder can only be at one place at a time. The location of each file and folder on the desktop or in a window was saved, as is the size and location of each open window, because objects remain where you left them unless moved.

It's not something that surfaces in conscious memory, but subconsciously this takes advantage of millions of years of evolution of the human brain to cope with and manipulate objecrs in the physical world, something other file managers don't do. Apple invested millions of dollars and thousands of user-hours of experimentation into making the OS take advantage of innate human psychology like this, something NO other computer manufacturer (including Xerox) had done at the time. It's a big part of why the original Mac OS was, objectively, the easiest operating system to use in the world (and far easier than many operating systems that postdate it including modern macOS).