Your comment made sense perhaps only twenty years ago. But today, everyone is desperate for this kind of info. Third-parties provide these services for free or close to it, especially to get access to the data stream.
Someone was on here a couple of years ago stating that even "line item" level data on your receipt is now being transmitted in a lot of cases, and growing.
The bottom line today—never expect a company to default to respect of your privacy. Simply too lucrative.
You're talking about something else there though: Data about what is bought and the demographics who buy it. They collect that data with loyalty cards, and the ones who don't use loyalty cards may collect that by some effective hash of a credit card number.
The store isn't tying your drivers license number and specific DOB to your purchases because you show an ID to buy beer -- that's a different kind of data and carries with it way too much potential for identity theft. Thinking that they want that is tinfoil-hat thinking. You can ask every single supermarket company if they do that and every one will tell you no. You can ask the companies which make the POS software if the scan ID functionality ties into data brokers and they'll say no. But go ahead and think that there are like 15 Fortune 500 companies all secretly doing this, even though not a single whistleblower has ever come forward. Of every engineer at those companies, I am not aware of anyone who has alleged this from a position of actual knowledge.
It's a several hundred billion dollar industry, in the US alone. Retail is definitely a source: https://market.us/report/data-broker-market/
Someone was on here a couple of years ago stating that even "line item" level data on your receipt is now being transmitted in a lot of cases, and growing.
The bottom line today—never expect a company to default to respect of your privacy. Simply too lucrative.