On the subject of why “we haven’t been contacted” I enjoyed Assistant Village Idiot’s image of a Martian observing those strange hominids on Earth, patiently checking in every 100,000 years:

For now, just keep thinking of that man from Mars dropping by every 100,000 years and seeing no change for a coupla dozen visits. Last two journal entries, at 200,000 years ago and 100,000 years ago:
21. No change to report. This batch got smarter than the other apes and then stopped dead. I think we should drop them.
22. There might be some hints of progress here, but I’m probably imagining things because I want to see it. Hope springs eternal in the Martian gazorninplat and all that.

As to intelligence: I suspect it is easy to feel smart if you only tackle simple problems. If you abstract away all the messy details about the 3% psychopaths and the old grudges and iron rice bowls then it is quite easy to devise schemes for world peace, and annoying that all these inferior intelligences won’t follow along.