Almost all so called AR glasses that are in the market now are working more like transparent LCD /OLED screens which doesn't have depth information but allows see through to see the object behind them. These AR glasses are just laying over the information from smartphones etc. on the transparent screens embedded in glasses so now it can be seen on glasses directly next to eye.
While it has it's own challenges in terms of optics they are not supposed to be confused with spatial computing capabilities that Microsoft's Hololens or Magic leap headsets introduced in the market which still costs thousands of $ yet has tons of limitations. Spatial 3d wearables are yet maturing and have long time for commercial markets unless say the rumored Apple glasses / headphones are launched in coming year which might introduce some breakthrough in quality.
In spatial computing headsets there is also information about the depth or the Z axis from the surroundings, which allows placement of 3D objects that are being rendered in real time on the wearable hardware on the 3d space seen through the glasses. This is a much more complicated problem where special optics is involved which is often glass waveguide optics which is a special type of glass that is created using special technics such as diffraction gratings. to be able to provide the stereoscopic depth. The waveguide optics is still a very hotly research area in terms of materials etc and is highly affected by the materials and other aspects.
If you look at the Microsoft Hololens or Magicleap headsets, the actual area that shows the 3D objects in the space around is super small like for example the size of a postage stamp which is sandwiched in the glass visor of the headset. So this small area severely limits the field of view and how much area can be used to lay our the optics. Remember this entire calculation of the 3D space around you is taking place in real time using the onboard computer on the headset, and that is why it is a very complex problem where lots of optics, materials, hardware, challenges exists. And that is why real AR glasses like Hololens will take time to mature and to come down in prices drastically, as we are now dealing with a spatial computer mean a computer that is mostly dealing with the 3D space in real time.
Until then you can feel happy about your AR glasses that lay over your phone notifications on your glass near eye.