Great insight from Benedict Evans:

I do indeed shop at one of their shops - or at least I think I do. I'm actually not 100% sure if it's a Tesco or a Sainsbury. I buy food there every week, but I don't consider myself their customer - at least not in the sense they meant it. Rather, it's one of 10 shops I go to in a week, and one of 20 errands I might run.

In other words, your customers' relationships with you are the only relationships you have as a business and you think a lot about them. But you're one of a thousand things your customer thinks about in a week, and one of dozens of businesses.