Seems like they're missing an opportunity to drive adoption of Office as an online platform. Why would I want to publish using Office instead of Google Docs when I can't assume that people I send the Office doc to will be able to edit it? Sure, Office is better, but not better enough to overcome that.
If it was free to edit, but $$$ to publish, Office 365 would be much more compelling. Especially since the situation w/r/t mobile looks much better than Google Docs.
Edit: My point here is about network effects, not whether the subscription is worth it. Office previously benefited from them, but it's vulnerable as a cloud platform given the free alternatives from Google and even Apple.