There's much less air traffic at night, and what traffic there is, is probably on an IFR flight plan.
But lighting would only really help VFR pilots if it was coming from above and they were looking down. Looking out and up from a small airplane cockpit to avoid traffic is really impractical. You're better off relying on ADS-B.
I feel like the damage done by the underside lights on airplanes is minimal at best, especially since planes, you know, move out of the way relatively quickly. The damage done by removing them can be tremendous.
I think there is a misunderstanding here. I was referring to the illumination of aircraft by lights on Earth, not lights on the aircraft itself. The light coming from Earth is wasted.
But lighting would only really help VFR pilots if it was coming from above and they were looking down. Looking out and up from a small airplane cockpit to avoid traffic is really impractical. You're better off relying on ADS-B.