Short version: Scientists use the scientific method to help them prevent huge mistakes that they can't fix. It helps them get an accurate answer to a question.
Long version: By using the scientific method, the scientist sets up the parameters of an experiment and outlines the procedure step-by-step so that any other researcher any where in the world can replicate his experiment and obtain the same results every time. When other researchers have done this experiment and obtained the same results, the conclusion can safely be included as a scientific fact and be added to the body of scientific knowledge. Without the scientific method, a lot of snake oil could be excepted as factual science.
