That "simply" is the issue. It
isn't simple to do actual AR glasses. That is what Cook had wanted, but the current method of mixing VR with camera views to simulate full AR was actually easier than AR projection on see-through lens, so it is what they settled for when they had trouble producing true AR.
Apple has paused development on the augmented reality Apple Glasses that it planned to introduce after its mixed reality headset, reports Bloomberg....
www.macrumors.com
I guess you could say that they could just use the Google Glass display tech, but that was a single screen in one of the eyes. Pretty cool at the time, but bare minimum as AR. This guy demonstrates it and refers to it as Picture-In-Picture:
And I don't think Apple really wanted to duplicate any of the Google Glass experience, especially Google's piece of that experience, though they are probably feeling a bit closer to that than they would have liked.