Why not? The goverment standardizes everything else, from screws to seat belts to yogurts, why not stop the crazy update-planned-obsolescence cycle pushed by commercial entities and agree on a "standard UI" for normal people?
The amount of unnecessary changes in UIs has become unbearably crazy. And since those changes are forced from all sides, there is no way to vote with your wallet.
Whoever wants to constantly relearn the same stuff over and over and over, and today relearn the Ribbon, tomorrow Metro, and so on, is free to do it. But normal, everyday folks should not have to deal with this shit. Computers are supposed to be boring, everyday tools to accomplish everyday tasks, not fashion statements.
If the commercial world is not willing or able to keep computers useful tools, the goverment has to step in and slow down the amount of changes and prevent the giant waste of tediously gathered know-how.