They tell a story I am interested in.
Its fine to put in all technical details and show how something is done, but if you have stories of people that did it my interest level is kept.
When a techique is followed by a story of some poor sap on his last dime and living in a car putting it to use and making millions, that is interesting. Its interesting because of the story and because I picture myself doing it too.
I would venture to guess that products with lots of good stories in them have more "stick" and get less refunds.