It shows you what kind of applications can be created with the new framework.
...and in this case, it's likely 90% DirectX. It's not showing an application with Metro design. If you include sample apps for a new development/GUI framework, then should show it off - this is the equivalent of showing off Metro by launching a video through the start screen.
If you want Metro, here you go (although these are just screen shots, not an actual demo):
It indeed does look great (note absence of bright green background and nice drop shadows - HINT), and this is the kind of stuff Metro is killer for.
But in this case, that design screams Tablet/TV. I'm interested in seeing how Metro could be used for more complex apps - apps where it's actually unproductive to require users to constantly scroll left and right. I don't believe Metro, as it stands, really fits that design - and there are thousands of apps that need to have that level of complexity.