A great, older, lower-tech example of this: I go to the store looking for Lays chips and they only have Ruffles. They're chips, sure, but I don't want Ruffles. I want Lays. I don't come back to that store because they don't have Lays.
I go to the store next door, they have Lays. It's exactly what I wanted. I now come back to that store frequently. Store 1 has no way of knowing what I wanted or why I didn't come back. Store 2 has no way of knowing why I suddenly started coming to the store.
I would still frequent Store 1 if they had the products I wanted. I only go to Store 2 because its (inadvertently) personalized for me.
"Gee the experience today was very personalized, I'm definitely coming back next time!"