Microsoft Office files are zipped XML these days, there's a standard and everything.

So? Doesn't matter. Git in that case still provides valuable historical archiving and versioning that is still more useful than the option, without it.

Plus, its chicken and egg. If the OS had a great interface to Git as part of its responsibilities in the Explorer/Finder interface, folks would be more inclined to use text-based file format standards that are coherent with the Git methodology.