How does it not solve the problem? The data shows up on the other end. The fact that you don't agree with the implementation is a different thing, but it does solve the case.
For small files maybe. As shocking as it may seem, most Dropbox users just have the free version, with very limited space. Same for Google Drive or One Drive.
Dropbox is unavailable to huge populations. also sharing private bits with a cloud service should not be necessary to transfer files locally between devices. at least user level file encryption should become straightforward on a mobile device which it is not today.
