1) NVG help you stay oriented whilst looking out of the window as you can see the ground surface quite clearly even from high altitude (providing there is decent moonlight or cultural lighting). This avoids the problem of perceiving false horizons due to confusion between stars and points of light on the surface.
2) NVG immediately highlight any aircraft displaying lights or using reheat. A view of the night skies over the UK using NVG will reveal many, many more aircraft than you could possibly see by day even in the clearest weather. Indeed it can become very confusing as you get very little idea of range. However if you have a radar or GCI service to help correlate the picture then you can get very long-range tallies (50nm+) using NVG.
Additional uses of NVG at high altitude, not relevant in this case, are close formation flying at night and joining AAR. Boom AAR such as practised by the USAF is often completed wearing NVG (most probe-and-drogue receivers will remove NVG once behind the tanker due to the lack of depth perception).