There are 2 things: as @Teleboy says, directly channeling customers' frustrations to the service provider and giving the impression that the company's actually interested in their insights.
The other aspect is that performance reports are increasingly based on customer satisfaction and the surveys are cunningly designed to give HR a massive assymetric information advantage.
So when it comes to salary increases/bonuses/termination, they'll filter the data and come back with "Oh look how poorly you're performing" if they don't like the shape of your nose...