Saving €65 Euro with Automobile Association and bad customer service

I got my renewal notice for the AA the other week. I checked online to confirm the price and then found something interesting. I could save get Rescue+ for €0 (value €65) if I was a new customer. So I called into the AA and said. Hey I'm an existing customer could I get the Rescue+ for free. No only for new customers I was told. So I said if my wife joined with me as an associate member (the opposite of the current arrangement) would I get the Rescue+ for free. Yes I was told.

So I did and I got the Rescue+ for free. For this year anyway. So why is it OK to treat new customers better than existing customers?