People have been doing a lot of things wrong for years, take a look at the butyl tape thread, I mounted windows for years with butyl tape, just like most everyone else, that don't make it right.
When you see failures as a rep, where you are called out to failures that could have been avoided, you learn to do the work even better. It's like the estimator who has to deliver cars to unhappy customers. If the body man or painter had to do that a while he would become MUCH better at the details. People with no experience what so ever see the flaws that a seasoned pro can miss. Believe me, that is a great education.