New Customers Wanted - Current Ones Do Not Apply

Just the other day, I received a coupon in the mail for a discount at a business I have not been to in over a year. I have also seen similar coupons in mass mailers from this company and one of its competitors.

You must be a new customer or have not been a client for over a year to be able to redeem this 20% off discount.

Funny thing is that once you become a customer, there are no deals. What do you think this trains the consumer to do?