That's a good question. Humans have a propensity to not believe words - until they do. I work with engineers fresh out of school, and tell them many times how things need to be done to work. They never listen and do it in a way that ends up costing time and money. Then they learn to listen. Experience is the best teacher - nobody believes words when it really counts, and decides to believe words when they shouldn't. Edit: also ask the q crowd why trump needed to lose the election....