I am repeating myself[1], but that premise just fundamentally doesn't make sense. A huge part of dropbox's value proposition is that all your files are on all your devices (and available to all your apps on those devices).

Apple's vision was/is of a feature that only works on your Apple devices. That's not the same thing at all, and isn't nearly as cool or groundbreaking.

[1]: http://masonmark.com/why-icloud-cant-ever-be-as-good-as-drop...