Top four reasons people suggest for why SETI hasn’t found a signal
1. "You’re counting on the aliens using communication technology (radio, light) that’s oh-so-last century. They will be far beyond this."
2. "If hi-tech societies or thinking machines were out there, they’d have colonized the Galaxy by now. Clearly, we’re alone… lone… lone."
3. "The aliens don’t want to communicate with us. Look at what we’re doing to the planet!"
4. "You SETI types are just looking in the wrong places. We know where the extraterrestrials are: on a planet in the Zeta Reticuli system."
I stumbled across "Majority Report" on Err America while on vacation in California. That's proof enough of aliens for me.
Although I have participated in SETI, I think it is somewhat far fetched to think that another civilization would be beaming radio messages our way. Even though we on earth are "advanced", we are listening but not, to my knowledge, attempting to transmit anything to possible alien worlds so why would they. Also, given the distances involved and the vastness of the radio frequency spectrum, it is not at all surprising nothing has been heard.
It makes sense to me to keep trying, but failure to find an "intelligent" signal means nothing.
"But I am not really willing to accept your premise, because it may well be that the means of communications they have are of a kind that we do not know how to receive, and that they would not have the means of communicating with sufficiently powerful radio or optical signals. That is something which, technologically, is too difficult for them but they would have some other means we would not recognize." -- Thomas J. Gold, 'Communication with Extraterrestial Intelligence' (Sagan, ed)