Actually it doesn't. There is enough background RF is completely hide intelligent RF. And there is enough matter in space to reflect and attenuate intelligent RF. We have absolutely no idea if RF can propagate even one light year through deep space. And even if it can, no idea if that's universally true for the majority of space. For example, deep space if full is highly charged plasma. We know this in of itself can completely attenuate RF. As usual, "science" makes these grand statements but fails to reveal it's based entirely upon conjecture and imagination with zero experimental evidence to support it and much body of science to invalidate it. Which completely ignores the fact that a technologically advanced civilization is extremely unlikely to use omnidirectional RF for deep space communication. And that if they really wanted to communicate light year distances, it's an all but certainty they would use highly specialized, directional RF. All which means, no one would ever see it even if they looked.