They attract a discount. We have mailing lists of over 30,000 people who have purchased our books. They are always eager to buy more. Many organisations and societies welcome talks by authors. This is a good way of making direct sales - usually autographed copies.
Most books are newsworthy in some way.
Articles usually include ordering details so that many direct sales can result. A good review in a national newspaper can result in literally hundreds of sales. They obtain books in volume and sell them on to independent booksellers. Advantage - copies of your book are sold in bulk. Also buy books in quantity to distribute to libraries throughout the country.