I do my grocery shopping just a few blocks down the road from my apartment, at Ralph's. When I buy things from Ralph's, I get Ralph's Rewards points, which are redeemable for a discount on gasoline at Ralph's fuel stations and participating Shell locations. I don't own a car, however, so I don't typically consume much gas, and my Rewards points are pretty useless. That's kind of frustrating to me, since Ralph's (and any other grocery stores offering fuel discounts) probably isn't selling discounted gasoline out of the goodness of its heart.
The more likely scenario is that they're charging a marginally higher price on their goods in order to subsidize the losses/reduced profit from gas sales, and people like myself end up spending more on their groceries for exactly zero benefit. This obviously isn't a huge cost to me and other shoppers, but it's more than zero. And it's not going to subsidize education or toothpaste or a gym membership, it's going to subsidize gasoline—a commodity that, while essential, is objectively bad for the environment and public health and probably not something we should be encouraging people to over-consume.
The extent to which this fuel reward trend has passed the point of reason is well illustrated by this green-minded promotion found on Ralph's website:
Unfortunately, this seems to be good business for Ralph's and their parent company Kroger, because their stores with fuel stations apparently do considerably better than those without. So while I can't blame them for offering this perk, it's nonetheless a pretty perverse outcome from a societal perspective. Along with the free-with-validation parking garage and its parking attendant employees (the costs of which are also baked into the sale price of my cereal and bananas), this is just another example of drivers being subsidized by those who choose not to drive, or can't.