is because the universe is very big.
Equally certain is the huge energy requirement to travel any meaningful interstellar distance and the stability of a civilisation prepared to invest in such a venture.
Given these three simple facts, we can draw three simple conclusions...
It seems unlikely that aliens would ever stumble across us.
If they ever did they would be here for a while.
They are unlikely to have travelled all this way for an elaborate games of hide and seek, or to play psychological tricks on american hillbillies.
Stop watching the skies, and get on with your lives.