Some people regard flashing as deviant behavior.
We, on the other hand, view it as a necessary element of construction. Flashing is a means of preventing water from making its way into areas of a building that could result in a leak. And where there is a leak, damage usually follows. In fact, many roof leaks haven't anything to do with roofing material. More often than not, they are the result of faulty, non-existent or poorly installed flashing.