There are quite a few people who cling to the file system as a necessary component for getting any complicated work done on a computer and who therefore believe iOS to be inherently unable to meet complex productivity tasks.
This is pretty wrong headed, because they think that they need the filesystem to be able to organize documents according to projects they are working on. But this can be done without exposing the filesystem to the user. And given how primitive the file system as an organizational tool is, it should not be too difficult to create something better.
The other advantage is that it allows multiple programs to cooperate on the same document. Again this is difficult to setup, and a more structured way to provide this power, with clear boundaries between the individual tools, should make it easier to use and also safer, as you could better control the content at these defined interface points.
In the end the file system enables some nice collaboration scenarios, but these are essentially hacks, and for most people it is far too easy to screw up with files. A more structured approach, where you can share documents in apps to a project manager, which then orchestrates everything, would be a much better way. It would enable advanced workflows without adding a burden to users with simpler needs.