This isn't a "non-focused" signal. This is being directed by an antenna in one dimension. A perfect antenna transmitting through empty space would send a signal that does not diminish at all with distance. The only attenuation would be due to imperfections in the antenna causing a gradual widening of the beam, and obstacles in the path of the signal.
Imperfections in the antenna, obstacles in the path of the signal, etc. From the The Hitchhiker's Guide to the Galaxy:
Space... is big. Really big. You just won't believe how vastly hugely mindbogglingly big it is...
My point is space is HUGE, and it would take a stupendous amount of effort and energy to create and send a signal which Earth can correctly receive. And that's even if you specifically focus it at us.
But why would anyone specifically focus it at us, if our own signals are not focused and quickly (quickly in term of universe distances) become indistinguishable from background radiation, how would they know we are here?
What I am ultimately claiming is that even if we have intelligent radio using alien life "near by" we still would never find each other. Because even if we both have a SETI equivalent, neither one of us would initiate the huge effort necessary to send a focused "Hello" signal which the other can receive.
Well, to start we could just send signals to nearby stars with planets. Obviously planets within 20 light years are the low hanging fruit. Since we know there's life on Earth, nearby stars might have a greater than average chance of harboring life as well.
There is at least one astronomer who's doing exactly that. I didn't find his name with a quick googling, but I think it was a Russian fellow. Naturally, not everyone agrees on the step from listening to sending focused, targeted bursts.
