Phone and headset AR have different affordances for different situations. Phone AR actually works right now and is deployed to everyone's pockets. And phones are much more capable input devices that headsets which allows for things like Pokemon Go. And you don't need to worry about obscuring the user's view so they can do full occlusion of real images and not worry about someone walking into a telephone pole. You can't do immersive, but immersive isn't the only or even the best approach.