Wine has a much harder task. Since the common Windows libraries are closed source and non-redistributable, the Wine project basically has to reimplement every API/ABI that Windows provides. This is a much larger and harder project.
It would be a nice gesture of Microsoft if they released some of the core Windows libraries as open source. But of course, that's not going to happen.
[1] This is of course much harder than it sounds.
A few years ago, I'd have agreed with you. I used to be a card-carrying Microsoft hater for many years. And I still agree that the chances of that hapening are small, but given Microsofts changes over the last few years and the stream of open source releases, who knows any more...
I don't think they will open source things Windows in a constellation where people could start making Windows distributions (which could lead to large incompatibilities) or run GUI apps on Linux or Windows.