1. Azure is handling the physics processing, not the Xbox One itself. That is a BIG difference since the offline version of Crackdown is a gimped version compared to the online version that has the processing.
2. The game itself has to be impressive, using it in something like Halo would have been better. Even though it's in an pre-alpha state, it could have looked better. We've seen countless tech demos before where the final product wasn't what the vision/demo had people believing.
3. You're relying on an internet connection to get the most out of it and a good connection at that. So that in itself already limits your consumer base. Even though it's becoming more and more minority, you don't want to alienate or limit millions of gamers by pushing an always on internet requirement to play a game at its best state.
I think this will be one of those nice to have things, but won't become the norm anytime soon.