Because the math on video poker is well known among intelligent people. Shuffling a 52-card deck and drawing cards are easy operations to describe mathematically. To have a high probability of winning at this game, all you have to do is learn to identify the machines where you have the advantage and learn to play the hands. The first part is very simple. The second part is not.
Singer argues that very few people can become video poker winners.
This is true. But almost everybody can get better. The information is out there. This book may well sell well. It is published by the people at Gambler's Book Club.