>>Because they might attract the attention of greater beings.

As a life form we don't seem to be taking any precautions to 'hide' from others.

Why are assuming others would like to 'hide'?

It could very well be that the only civilizations that still exist are the ones that are good at hiding. All the others (even if they are the big majority) might have been destroyed after giving a signal of life/existence.

Greater beings are nothing to worry about. They remain undetectable in order to preserve the lesser beings as long as possible.