They would check your fluids, clean your windshield and it was normal to tip them. Self service stations were at first an options and were cheaper. Sound the same? You only get a discount for self check if you steal, and Iβve never tipped a cashier at a grocery store.
Not to mention gas pumps got a lot simpler, and added auto-shutoff. The cash register at the grocery store is requiring you to do exactly the same job they used to pay someone to do, for free.