[caf]

There's no need for it to be a completely separated interface, though - in theory, at the top level you could have "Files", "Music", "Photos", "Mail" and so on. When you descend into "Files", you see the root of a traditional filesystem, when you descend into "Music" you see a music-specific interface.

[ugh]

Would you really want your file browser to become such a monster?

[caf]

It's really more of a question of "Why does my shell currently privilege file browsing above music or email browsing?" I would contend that it's for historical reasons more than anything else.