Sure, but you don't necessarily need a hierarchical order. Of course the whole desktop computer is a metaphor of the desk and the first commercially successful

Sure, but you don't necessarily need a hierarchical order. Of course the whole desktop computer is a metaphor of the desk and the first commercially successful graphical interfaces resemble a desk. And GUIs are what most people use most of the time, even most devs tend to start their terminal from the desktop in a window, which appears a bit like paper, laying on the desk. It's interesting that only few graphical operating environments break with this convention. It seems there hasn't been much conceptual innovation in the space of "desktop computing". Even the tablet seems to represent either a piece laying on the table or the table itself, depending on the size. It should be more efficient to design systems based on the available digital infrastructure, instead of designing them based on partially obsolete office table infrastructure.