Every loyalty card purchase generates granular data about your consumer habits. Where you shop, what you buy, how much you spend. Coupled with age, income, race, sexual preference, political affiliation, and more makes for a deep insight into your inner life. These businesses don't operate out in the open so the general public is mostly ignorant about what has been going on. The level of invasiveness that has existed for 30+ years should not be underestimated.