That's how they get you

I recall being a small boy and riding in the car with my father. We were very hungry and he stopped in a gas station. He got something quick to eat, I don't remember what, and he shared some with me, so that we could make it home and eat properly.

I saw a rack with salted peanuts hanging on it.

"I want some of those peanuts," I said. We were, I recall, back in the car when I said this. The peanuts were visible from the car, on a rack.

"No," my father explained, "The peanuts make you thirsty. That's how they get you to buy a Coke."