A lot of good comments have already been made, but I'd like to mention another issue (that is by the way quite an old point and not original to me. I think Martin Gardner made the point many years ago, and Michael Shermer is often fond of it.) People are overactive pattern seekers. We seek to see large patterns where they don't necessarily exist. Moreover, this gives people comfort because people don't like a complicated, difficult to understand universe with lots of random events. Take that with a healthy dose of confirmation bias and you get the end result.