It's a perfectly good reason because when you're flying, you're looking at instruments and the outside world, not focusing at your nose. If they mask area in the center of the screen, I can see masked area 100% of the time and it's going to be annoying. We have two eyes and our nose isn't really blocking our vision, blob on the screen would. Even with OR.
They need to model things that pilot is experiencing, but you in your chair don't, such as hypoxia or G related effects. Sensory adaptation, where you stop hearing repeated sounds, is already a part of your brain™ v1.0 firmware. ;)