We are early in our "Space age". It's possible that inexperienced civilizations emit their position only to start hiding after realizing the dangers. Other poss

We are early in our "Space age". It's possible that inexperienced civilizations emit their position only to start hiding after realizing the dangers. Other possibility is that we are in a short period until we are wiped out because we broadcast our position. All of this would drastically reduce number of visible civilizations at any time making the detection of civilizations much less likely.