We hear it all the time: "My father (or uncle or cousin) has been in the business for 50 years and he always did it this way. He taught it to me, so it must be right." Or: "I know what I'm doing and don't need any more information."
Have you ever gone into a floor covering store, a tile outlet or a big-box store and met the super salesperson? You know, the one who says, "Sure you can tile over oriented strand board (OSB). I do it all the time. And sure, throw down a sheet of Luan underlayment -- that'll level your floor and work real well. Caulk, what is that? I never caulk any joints, because they don't look good and aren't needed anyway." In truth, these assertions are all fallacies of the uneducated.