I understand that the WP8 emulator requires Windows 8, however I don't understand why Windows 8 is required if you plan to use a physical WP8 device. There are hacks around the web where people successfully install the WP8 SDK on Windows 7 and everything works fine in VS 2012 other than the emulator.

What possible reason could MS have to require Windows 8 for those that don't need the emulator?

Is it really just to force people onto Windows 8?