I think a big problem with apple doing this is that they literally decided to make the body of the device out of steel, which is much heavier than other materials like plastic. The bigscreen beyond is the currently lightest headset, but the only things in the headset are the displays, processing and tracking are outside of the headset and no passthrough cameras. So basically with current lens and display technology its still not possible to get glasses like formfactor in VR headsets, let alone with integrated cameras, processing, movable ipd, eye tracking, etc.