Traditionally sales people have been conditioned to believe that if the buyer likes them they’ll buy from them. While the relationship is certainly an aspect of the buyer seller relationship it can't be the only thing. If the sales person never understands the buyer's actual business needs then you can have the greatest relationship in the world and it’s not going to get you where you want to go.
The successful seller has to do far more than simply cultivate relationships. The best way to establish a strong relationship with your buyer is to help the buyer visualize a solution to a problem with your help. Sales people who help buyers solve problems gain the best relationships long term.