The simple answer is that MS had to add all those buttons in the ribbon to make the UI more touch friendly. You cant right click on a tablet with your finger.
Moving to this design is a step in the right direction. They need to do more - like ax the filesystem altogether (rendering this step meaningless), but that's another story.
There are more elegant ways to add touch-usable capabilities than gobbling up real-estate (iOS implements the "context menu" as a long-click meta-mode). You could also use persistent buttons like PalmOS/Android.
Discoverability is a prime way to keep things elegant (ie, don't push it in a user's face - let them find it easily).
Of course, if Microsoft wants to address BOTH touch and desktop, then I wish them well... that's a herculean task and I don't think any solution work well for either.
The problem here is really the ribbon itself. It is ugly awkward and hard to scan quickly due to it's inconsistent layout. I almost never find what I'm looking for without looking two or three times and I'm a regular user. Yes tablets need buttons to touch, what they don't need is a cluttered ugly ribbon.
If they want to go touch they should be getting rid of the file system, not making it easier to manage. Touch devices are appliances. The reason I left windows in the first place was because I was sick of managing it. I'm certainly not going to pay money for the joy of managing an appliance.
Moving to this design is a step in the right direction. They need to do more - like ax the filesystem altogether (rendering this step meaningless), but that's another story.