To my knowledge retailers have no benefit from service related work - its a service for the retailer's customers. Some retailers charge a small fee for handling such work. Nikon has special customer service for retailers permitting access to inquiries in come circumstances.
I've had retailers involved in 2 or 4 service claims. Both were with new merchandise. On the first, the retailer had no leverage and actually slowed down the process. On the most recent, the retailer was able to call and accelerate my repair (but it was a brand new 600 f/4 that had never worked at all).