I should just add also, there has been quite a lot of rigidity with this. A lot of "filetypes" actually have filesystems inside them.

Hell, HTML files encode a tree. Hypertext links are like filesystem links across the network.

The technology is still very immature. The benefits of extending the filesystem have yet to be realised, and I'm already 40 years in on this from my early experiences with simple tape recorder soud modulated recording systems, and better ways already existed but just have not been implemented, since at least 30 years.

There isn't enough computer programmers, and partly this is because programming languages are overly complex and build systems unfriendly and labor intensive.