Why don't people use common sense? Do they even have it? And yes, I do use it. And I am smarter than you.
Let's take the Ancient Aliens theory. If you're not familiar with this, it's a bunch of people that believe that aliens came down and taught the Egyptians how to build the pyramids, among other stuff. Here's a quote from Wikipedia (I know, this is supposed to be about using common sense, and here I am taking stuff from Wikipedia, but it's late, and I'm tired) about a show on the topic: