I just had a thought. Could it be all those aliens that have telepathy just have a really good wireless network? All they have are implanted headsets and a small microphone that would would let them subvocalize. The reason all these different aliens can't talk to each is because they all have different service providers. I guarantee you that the wireless company on Remulak 5 doesn't play nice with the nubile women from planet Playtex.