The thing you have to realize is that for all intents and purposes, Microsoft considers the desktop to be "legacy". All development moving forward will be focused on Metro, since that is what allows cross-device compatibility (ARM, phones, etc..).
They knew they couldn't just kill the legacy apps, but the whole point of Windows 8 is Metro, and even though 8 brings lots of other nice reasons to upgrade from Windows 7, Metro is what they consider the wave of the future. x86/64 based versions of windows will support legacy apps for a long time to come, but Metro is now considered the primary API.
So in Microsoft's eyes, disabling Metro is effectively Disabling Windows 8. If you don't want Metro, then you should stay on Windows 7.
Windows as we knew it is dead. Long live Windows. (more like in the Monty Python, Bring out your dead sort of way though)