They just know it does, so they use it. Reynolds called it a sort of phenomenological operationalism. I guess that's a good name for my philosophy. I think of these ideas as tools. With any given task, some tools will be better than others.
Some tools are effective for many different tasks.
For example, exercise. In the book, Think and Grow Rich by Napoleon Hill, he describes 13 principles. One of them is autosuggestion . The principles are excellent, but his explanation of them, his answer to WHY it works, seems silly. That was a popular theory of his day.