[brewdad]

Are you changing insurance companies regularly? Why would an insurance company have any reason to reduce your rates unless legally required to? Even if they've been overcharging you for years compared to competitors, if you aren't calling them up and threatening to change insurers, why would they ever give you money back?

[frockington]

Probably the same reason airplanes have frequent flyer miles. If a customer has proven to be low hassle you don't want to lose them

[extr]

Yes, if it gets to the point where they've already shopped around you're going to be paying a much higher price to retain that customer, than if you simply gave them a reasonably competitive premium or deserved discount. Insurance companies are not like cable, customers are free to switch to one of many options at any time. Acquisition and churn costs are huge problems.