Have you not noticed that the OS no longer provides the features of an Operating System? Wouldn't a "true OS vendor" have added peer-to-peer and file-sharing-across-multiple-networks/nodes to their feature set by now?
What I think has happened is that the OS vendors: Microsoft, Apple, and to a much lesser extent, the Linux crowd - have forgotten that they, themselves, define what the "OS" is, but it is the users who require it.
Why on Earth some OS vendor hasn't solved this mid-80's problem of network file sync, is simply this: there is no profit in it. In short, the bugs and holes in featuresets provided by the current OS vendors have been filled in by an industry far too furiously devouring itself to care that they've gone off-task.
The fact is, we should've had DropBox -like features integrated into our OS's, already. We should definitely have had Bittorrent-sync like features, implemented already. We should definitely be demanding these sorts of features from the OS vendors - but do we?
The answer is, no. We don't. Because, every 5 years or so, newcomers to the computer scene, the teenagers of the now who will be the next-bright-new-thing of the morrow, fail to keep up with the state of the art just well enough that they end up re-inventing the very thing that their much-hated "prior generations" have been, literally, on the cusp of inventing .. for years.
So yeah, we have this situation because there is no longer a 'true OS' out there in the world, but rather 'front-ends to a business model'. Maybe that will change, who knows, but I bet that before it does, the words "operating" and "system" will have to suffer a bit of re-definition, here and there. Or wait, maybe that is exactly the problem ..