Why did Mark Twain use superstition in Huckleberry Finn?

Well this is quite a difficult question but the examples could be Boo Radley and the Radley house as the children become quite obsessed from it and they are very superstition. They believe that anything from the yard is poison. They are also superstitious about the stuff that they find in the hole in the tree from the yard as they think the Indian head coins give good luck.