Why Would You Get Hit By a Bus? (And other uses of cliches)

Today must have been the day for buses.  On at least three occasions, I read the phrase, "In case I get hit by a bus."  My mother used to tell me that.  Only she added that I had to be sure to be wearing clean underwear just in case. I commented to my husband that I was reading a lot of cliches lately.  He asked me, "Why do people think they would get hit...