"Common sense" is the bane of our existence.

There are so, so many things that are completely wrong but people don't look into because they want to be lazy and chalk it up to "common sense". There are so many problems that can be solved but aren't because people are willfully ignorant.

This is the difference between unintelligence and stupidity. Unintelligence is genetic. Stupidity is willful. And because of "common sense", we're all stupid.