I think you're incorrect on your logic there. Also you have to realize there's no native Metro file explorer, so "sharing" that file isn't as easy. It should be able to be sent to email application.
I'm really glad I subscribed to this thread because I figured it'd be getting some good responses.
I think this is a really good example of the lack of integration between Metro and desktop UI. I feel like Microsoft is pushing for Metro, and I prefer Metro, but the problem is, it's not very productive. The reason of that is because Microsoft LIMITS the way developers can interact with the system, so they just rely on legacy apps to handle this. It really does feel like a Windows 7 with a Metro shell sometimes.
I would love to have all of my regularly used desktop applications as a Metro application without losing any functionality. I think a lot of Metro apps over simplify, so I end up just using the desktop version (see Skype) or use a web version (see Outlook).
I think Windows Blue is a good step, and I really like Windows 8. They just need to up the productivity level of applications and stop trying to limit their capability for security, instead make security an operating level thing instead of managing it through limiting developers. And make Metro apps more productive!! Stop supporting legacy, it will drag and hold you down in the end.
Another example is the fact that you don't get desktop notifications Metro side, and you can't have Metro apps pinned in the taskbar(without 3rd party).
Again, this thread is just a bigger example of how desktop is just a placeholder and they did no work to integrate these 2 pieces.