Quick question: why aren't there any code samples [0] in C/C++? It would be nice to at least have a documented C++ WinRT API to work with for those of us that still write native desktop applications/services. I'm sure other folks across the company would agree ;)
Take this as my own personal opinion, but before I went back into engineering, I worked with a bunch of developers out there to integrate with all kinds of our stuff - and outside of game development, C/C++ isn't the most popular choice. We have some code samples [0], but I see what you mean.
The office team moving away from the old plugin model and opening up the gates for JS apps and REST APIs made life dramatically easier for a lot of folks. So I assume that samples were written with the most popular choices in mind. Internally, C++ is king [0], of course.
It's also worth pointing out that we always accept code samples from the community :)
[0]: http://dev.office.com/code-samples