How many people do you know who could, months later, find the receipt for a battery ? I suppose there are people who would carefully file it and then remember where they filed it, but I’m not one of them. Most of us are not, so the store is on to a good thing. Lots of good public relations at very little cost.
This is the “let’s do lunch” of promises. If you call me and say “Six months ago you invited me for lunch. How about Thursday?” I would be in shock. Did I really invite you for lunch? When, exactly? I would not actually ask you to prove it, though. Even though there are no conversational “receipts,” half-hearted invitations are also good public relations at very little cost.
We make lots of easy promises: I’ll do this dishes when I finish watching the game; I’ll tidy my room after I do my homework; I’ll keep in touch; I’ll always love you; I’ll stick to this diet; I’ll learn Spanish, and so on.
Unlike the watch battery receipt, we don’t expect to have to prove that we made the promise, or even that we meant it. When my son was a teenager he explained to me that when he said he’d clean his room he meant that he’d do it at some point, but not right away. He’d do it on his schedule, not mine. It hadn’t occurred to me that there were variables like that in the agreement.
If I went back to the watch battery store, and they said they meant dog years not human years, and now the time was up, I’d feel cheated. But even at that, I’d still need the receipt, so it’s not going to happen