This is it! I was thinking about this a few weeks ago. None of the big tech gets this. If this works, damn, that's the future wearable I want. But why glasses? can you do this equally well with a earphone form factor?
It must be because eventually they're planning for them to be augmented reality glasses -- being both the input and output device is such a natural extension of this, they must have thought of it.
Glasses are a great way to provide output back, via an AR display, and also offer more real estate to fit the electronics and antennas in.
Headphones are also a great way to provide output back, and people are already used to wearing headphones in environments where speaking to their device doesn't make sense. You can put antennas in a boom, and nobody would bat an eye because many headphones already have boom mics.