The reason why sales can be such a challenging job is because often salespeople are selling at a huge disadvantage. They are approaching people who most likely have no idea who they are to get them to buy a product that they don't (know they) need.
But the real problem here is that salespeople are trained to think that the sale happens when they approach and talk with their customers. They think that selling is essentially a verbal exchange, where they address customer issues, provide convincing reasons to buy, build trust, etc.
In reality, most sales happen before the actual sale. The curious customer who comes to the store or website - she's already on the cusp of buying. She just needs someone to smooth out the process, make it as painless as possible.
Salespeople are not persuaders, but facilitators. They are there to prevent buyer's remorse. To allay any last-minute fears or doubts the curious customer may have.
This is why everything in a business has to be geared towards the sale - product development, reception, marketing, even accounting. If you build curiosity into the product/service, then the sales will come.