And absent from (or at least heavily obfuscated on) the mobiles and tablets young students use as their primary computing devices.

Except games consoles. And tablets. And phones. And quite a lot of online services..

Phones have files and directories and there are several apps targeting normal audiences.

In other words, "that's how we've always done it". Is the justification for continuing to do it that way when the very foundation of that is based on outdated abstractions? As mentioned, there's no tangible reason for using directories and files as organizations except that we're fitting modern paradigms into existing ones. We're retro-fitting them to a system that existed because of technical limitations that don't exist now, for some reason.