Eh, it’s food, there’s only so much I can eat. So it’s not as if I’m going to suddenly buying more food because I’m walking around the grocery store. Even if I did, it would be longer before I’d need to go back and get more food.
I think it’s more down to certain brands paying the grocery store to have their products placed in more prominent places. So yeah people will buy different things, but not more. But if it’s more Brand X instead of Brand Y, Brand X makes more money and kicks back some of that to the grocery store.