Oligopolistic producers and retail price wars
A producer won't always want the retail outlets to compete on price. This is the reason for minimum resale price maintenance. By competing on price, it may be that the retailers competition amounts to something closer to a zero-sum game. Supposing there are some consumers who value something like service, it might be better for joint profits to provide good service and thus bring in new consumers. You might imagine two stores selling electronics. The stores might find it best to cut price to pull the customers away from the other. The producer would rather there be good service, display models, helpful employees, etc to bring in new customers.

Reference: Winter (1993)