, I think the point that Purple Buddha
was making is that we have been looking for intelligent life for a very short time, relatively to the lifespan of the Milky Way. I mean, it's only been in the past 15 years or so we've even been able to detect other planets, which even then have generally been the superJovian type planets (though we have been detecting rocky planets now), so if that's as best as we can see right now, it's quite likely we don't even have the technology to even spot civilization in other systems. It may even be the case the only way to know for sure if there's civilization is to go to their system and learn 'first hand'.
Expanding Buddha's analogy, imagine if the cats were blind and could only find each other by literally bumping into each other, which at this scale, is probably a close analogy. Either that or the cat that represents humanity is both deaf and blind, and can't tell that the other cats can see us :P