I guess some people don’t know that every time they shop, a detailed profile of them is available to the retailer. They may know what you browse for online, what you browse on your phone in the store, where you live, where you work, which other stores you’ve visited, which brands you’ve looked at, which particular products you’ve looked at in other stores, where you’ve moved to and from. 

If you go to a coffee shop, the shop may track how long you’re at that location, what you’ve ordered, which other shops you frequent etc…If you got an email from Starbucks, they will know if you’ve actually visited a starbucks location after seeing that email.

If you go to a store and look at some item, you may come home later to see an ad in your inbox from that brand or delivered via push notifications.

They use bluetooth beacons, “free” in-store wifi and cell tower coverage to collect all of this information. In stores they deploy computer vision to do much of the spying.

Worst part, this is all at least 5 year old news and who knows what things look like today - my guess is very dystopian.