The mobile authenticator is supported on more than just the iPhone. A lot of phone models are supported. That said, if your model isn't supported, then yeah it's a bit much to ask of a customer to upgrade their phone to play WoW.
Including them in physical copies of the game would be useful. They included it as part of the loot swag at Blizzcon '09 and '08 as well I believe. Don't see why they couldn't for boxed copies. Who knows, maybe they will for Cataclysm.