The only catch here is that such messages would be prohibitively costly (power wise) to transmit uniformly in all directions. They would be point to point to re

The only catch here is that such messages would be prohibitively costly (power wise) to transmit uniformly in all directions. They would be point to point to reduce the power, required to transmit, and increase privacy. It's difficult to intercept line of sight communications and it's unlikely we'd fall on the line of sight of two hot spots of intelligent communication in all the vastness of space. Even if they broadcast, I doubt it would be so completely uniform in all directions through long periods of time so as to appear as background.