Salespeople obviously understand the value of sales. They have a product or service that they know can make your company better, and it's their job to make you feel the same way.
But from the other end, it's easy to see a sales call as an interruption, especially if it's not your explicit job to listen. Many avoid sales calls, others dismiss them, and some resent them.
Perfectly understandable, because we all have a lot to do, and listening to salespeople isn't necessarily top on the priority list...but isn't it everyone's job to keep an eye on what's new? Isn't it the entire company's responsiblitity to keep an open mind on ways to improve, to innovate, to save money?
It may not be part of your formal job description, but listening to some (not all) salespeople IS part of your job.