I can kind of answer this question. For a year, I worked at a big box store where you can “save big money”. They had periodic training and one of the modules was on their store card.
The question was, “Why do we want people to have our card?”
I replied, “Because we don’t have to pay the standard processing fees.”
“No, it’s because of loyalty. If they have a [big box store] card, then they’re much more likely to spend their money here instead of [competitor].”