Who knows! Maybe same reason some wildlife photographers will set up blinds from which to shoot, even when the animals can see cars going by on a nearby highway or planes flying overhead.
It's not las if a monkey is ever going to comprehend the motivations behind the photographers or the drivers anyway even if you tried to explain it to them in bananas.
Alas, we are not monkeys and can reason. Maybe not wisely but the ability is there.
Not disputing that there may be intelligent life among the stars but a few flashing lights aren’t convincing.
Extraordinary claims demand extraordinary evidence.