It does. I think the assumption here is that the author is the only contributor to the document. Exporting into a Word doc would serve the same function as exporting to a .pdf, others could read it and even mark it up, but the author would have to make the noted changes in their original plain text document themselves.
Once the work has moved into a Word file, isn't that where it stays? Editors and publishers often make heavy use of features like track changes and notes. Doesn't pandoc lose that information?