My view on this issue is that civilizations that are higher than human science and technology choose to observe or be silent in secret, while civilizations that are lower than or equal to human science and technology continue to explore in a limited space like us.
The former is more likely, just like in the animal world, we will take pictures of lions preying on zebras but will not intervene. Compared with those alien creatures who are taller than us, there are too many killings on this earth, and just people regard killing as the foundation of a country-the army.
If I were an alien, I wouldn't touch humans rashly for the simple reason that I was afraid of being dissected.