Did you read the post that I quoted in mine? That's why. Completely shutting out reality is just a no-go in real life. A phone is already bad enough, why make the problem even worse? Imagine wearing these on a train? That's the only daily use I can think of for them. People bumping into you, blaming you, well, it's probably your fault for wearing such an obtrusive thing on your face anyway.If it's screen space you want, which gives more? A phone that can be unfolded to double its screen space, or a headset that effectively turns your entire field of view into a giant display which dwarves even the largest TV you can buy?
The Apple advertising team are having a very difficult time trying to portray why this is useful. This is a solution looking for a problem.