When stores know who you are, they can offer each customer a different price. The asymmetry of information means this generally benefits the store and hurts the customers.

Once the practice of price discrimination among customers gets big enough, there is no difference between "rewarding customers A, B and C with discounts" and "imposing a higher price on customers X, Y and Z" except presentation.

You can thwart this by paying cash, anonymously. Please join me in defending the right to pay cash, in insisting "cash or no sale".