There’s a reason they are called, internally in business parlance, “Loyalty Programs.”

The point is to get you to come back. Using the Kroger card at Kroger gets you discounts. Or rather, gets you their regular price; their non-card prices are artificially inflated in most cases. So consumers form the idea in their heads that those discounts have value and will return to that store to take advantage of them. This is played up by the retailer in their marketing, who will use terminology to try to make you feel special about the program. (As if it’s not offered to absolutely everyone who will listen, and also everyone who won’t.) Look for words and terms like “exclusive,” “VIP,” or “members only,” or “just for you.”

The buy-stuff-to-get-rewards schemes are the worst, because they prey on the inbuilt sunk cost fallacy neurons in people’s brains. You are statistically likely to buy and spend more if you think you’re going to get something back, or spend a little more than you otherwise would have to meet whatever threshold they set to get the next reward. Even if the reward you get back does not actually match in value to the extra amount(s) you spent. (Hint: It never does. The house always wins.)

Nowadays, of course, they also track and record your purchase history and sell it to whoever will pay. Possibly anonymized in some way, but probably not.