Since people use "Cloud" as if it refers to only offsite storage that is what it is to them. The rest of your definition is unimportant to them.
They are just interested in using it.
Dropbox is easy to use and provides files on ones desktop, i.e. there is a comfort level in not having to trust (yet) that the "cloud" vanishes with all "my" information.
I don't use dropbox so correct me if i'm wrong. Isn't dropbox an application with it's own dedicated window ? In other words not part of the native Finder.
Now Imagine a dropbox concept that is integrated into the Finder window.
This is it.