(1) all AAA games (working on the GTX 9xx or 1xxx) are still subpar to the reality, and they're disspating hundreds of wattage. It's not possible to put it into binoculars.
Now, yes, I know that at the speed of light (or more properly the speed of electrical signals) having a PC 3m away is only about 10ns, which is not going to be noticeable.
But there will need to be translation on each end to send a signal that far away, such as conversion to / from HDMI. If the embedded processor in the headset is directly connected to the LCD, that type of conversion eliminated. Ditto for cameras and other sensors needed for position tracking.
To reduce latency, developers are counting microseconds these days. Crazy.
If you do something 10,000 time every frame that takes 10ns it's still only 0.0001 seconds and no you don't need to make that trip 10,000 times sequentially.