10 Theories Why We Haven't Discovered Aliens Yet
4. They're Ignoring Us
In They're Made Out of Meat, the aliens look at humans (once they are done deliberating about what they're made of) and decide to ignore them. Their job is to make contact with any life they discover, but they can't get their heads around contacting a life form made of flesh, so they mark the sector as unoccupied and move on. So, what if aliens discovered humans decades or even centuries ago, and decided that they weren't worth the effort of talking to?
That's a little hurtful to the collective self-esteem of the species, but if a super-advanced race of aliens that had outgrown constant war and conflict looked at Earth, maybe it's not unreasonable. Or, it could be like the Prime Directive in Star Trek, and they have to wait until mankind develops sufficiently. The downside to this theory is that it does not seem likely that any alien would think another type of life form is completely unremarkable. Either way, they know humans are out here, and it's a coin toss as to whether or not they're watching.