The "files and folders" hierarchical tree model for a file system is one where I wonder about the limits or effectiveness of the skeuomorphism approach to convey such a concept. If you're coming from a place where information was generally held and organized on paper, it _should_ be natural that you can group files within a container like a folder, and the kind of folder the iconography showed should be able to contain sub-folders.

While many did pick up on the idea, where were the shortcomings? Were the early graphics not enough to build the mental link. Was it the common grid view of icons. Was it the icon being an abstract thing you needed to open to see the contents instead of looking at it directly (as previews on the icon which came later), was it things opening in separate windows. It's not as though other more visually 'rich' methods to show a file system such as 3D or animated took off.

There's also the modern version that gets brought up occasionally where people who are using devices with mobile instead of desktop OSes apparently don't know how to work with file systems to manage data, and presumably they'd have even less exposure to the physical paper concept that inspired it.