As Victor stated, the original audience for this book was the American salesman.
Unfortunately, the word "salesman" doesn't garner much respect anymore, but proper salesmanship is an art.
Discovering what the person wants, and then showing them how you can meet their need is what true selling is all about.
Unfortunately, everyone gets a bad name when a few just try to make you buy something you don't want or need because of their own selfish desire.
When I was learning how to sell, this book taught me the proper way to do it.
And, inadvertently, I learned how to generally be more likeable to others.