The same reason as having batteries in your phone, even though you can use it while plugged in. Most people use VR while moving around, and mobility is much easier when you're untethered. If you're going to make an all-in-one headset, that hardware should probably be one piece.

Hopefully they just drop the standalone element altogether and go all-in on a nice tethered experience.

> Most people use VR while moving around

That's if you're into gaming which Apple isn't.

I suspect the future of VR is going to be at a desk, sofa, bed etc. with virtual screens, meetings, educational lessons, movies etc.

Well good news then! The future of VR is here, and you can already watch movies, educational lessons and virtual screens at your desk, bed or sofa. You don't need a headset to do that, even. You certainly don't need to spend $3,000 on it.

The problem is, none of that stuff is appealing. It's not only not a killer app, it's not even a profit driver. Games move some units, but even that is arguably clunky when you're not fully leveraging 6DOF.

So, what's the point of making a mobile headset that's not intended to be moved around? Why tether a headset that could be plugged into another machine altogether?