Legitimate question: At this point, what could a loyalty card possibly measure that isn't already measured on a bigger scale?
The cc/bank provider already gets an itemized bill, and they get it for everywhere you shop as opposed to a single store (so a superset of this data is already collected). This is in some (most?) cases already shared with stores, and even if it isn't, what can a store do with it the bank/cc provider can't do worse.