Why have night vision if you never look out of the cockpit anyway.....?
You jest but quite honestly, is there much benefit to staring out into the dark when your eyes are not really focussed on what’s out there? And even if they were, what are you going to do about it? We have TCAS, ATC, etc. and it is difficult to impossible to tell, unless your are very close, whether someone is above/below you to any degree of certainty. Are you going to deviate from your clearance (and possibly cause a coming-together) because of some random lights in the sky?
In the middle of the night I prefer a bit of illumination in the cockpit and some conversation to keep me awake...