Some retail stores use your phone to track you while you’re in the store, so they might even know how long you pause to look at a display, or when you take something from a shelf and put it back. They have information from your actual purchases, and if you use a credit card or a store loyalty account, it’s quite easy for all of that information to be linked. They also might have additional information that they’ve purchased about you and your shopping history.
Amazon now owns Amazon Fresh and Whole Foods, as well as Zappos. They have my extensive Amazon shopping history. For people with Amazon Prime, an Amazon credit card, and those who use Amazon for health care needs, they have even more . They know what you read, what you eat, who you send gifts to…. It’s beyond creepy sometimes.
https://lifehacker.com/how-retail-stores-track-you-using-your-smartphone-and-827512308