Not exactly but it’s part of it, you can also use people’s situations (weak points) to sell. For example, if you work in a hospital(not necessary), you can write a book about “How to improve your baby’s IQ while it’s still in your womb”. The pregnancy is the situation/weak point, and no mother wants a dull child, so your product has a high probability of selling out fast. So there are different kinds of market/crowd.