I'm told that librarians like trailers because it allows them to get a get a sense of a book quickly before making a purchase decision for the library. (jakonrath.blogspot.ru)
When making a purchasing decision on food, consumers have to trust that the food manufacturers have delivered a product that is safe to consume. (refrigeratedfrozenfood.com)
When book buyers access their ordering database, the preview will appear with your book's ordering information to aid buyers in making a purchasing decision. (authorhouse.com)