Increasing resolution increases computational complexity. This is especially true with the 100hz refresh rate of the display. Current Vision Pro resolution is higher than 4k. Imagine trying to build a 8k 100hz PC. You couldn't even use Display Port or HDMI to transport video data because those channels don't provide enough data.

With the questionable state of Moore's law, and the battery powered nature of the device, it might be awhile before tech catches up. Faster components would use more energy. We need to balance performance with battery capacity, and I expect the product that really catches on will have more of both.