At first I thought this too, but now I prefer for my file storage to be platform agnostic. For instance, if I decide to switch from iOS to Android in the future, I can just download the Dropbox app instead of implementing workarounds.
For me it's beyond that. I make constant use of my Dropbox files from Linux boxen, my iPhone, and a couple of MacBook Pros. I severely doubt iCloud would ever support Linux in a meaningful way.