How many times have you gone outside after dark, looked up, and seen a jet flying overhead? The only reason you even knew it was there was because of its flashing lights. If it wasn’t for the lights, you wouldn’t have been able to see it at all.
When people see UFOs at night, the UFOs are always highlighted in some way, whether it be streaks of light, flashing lights, or hovering lights. That’s how the people can see them. If the UFO didn’t have any sort of lights on, people wouldn’t know they were there.
If a race of beings possessed the technical capability to create interstellar spacecraft, they certainly would also have the ability to turn the lights on that craft on and off when they wanted to. So when the lights are on, when a UFO is emitting some sort of light, it’s because those piloting the UFO want there to be some light. They’ve chosen for the craft to emit light in whatever form it takes.
If UFOs didn’t want to be seen, they wouldn’t have their lights on, and yet they do. Whatever the UFOs are, when they’re flying around at night it’s clear they want to be seen.