If there are that many inhabitable planets then even if only a tiny fraction developed intelligent life that would still be a great deal of planets. Where are all the signals of intelligent civilization then? We should be bombarded with radio waves shot off from long extinct, not so long extint, and even perhaps a few still extant civilizations. The silence is deafening.
I had a little idea about that: if you were on the moon, and pointed a sufficiently sensitive antenna towards the Earth, and tuned to Channel Two on the TV... you'd get random noise, because you'd be getting all the separate Channel Twos in the hemisphere facing you at once. So maybe the alien signals are there but in such quantity that they're interfering with each other and mutually masking their non-random nature.