Maybe you've been to a mega-chain store, and maybe they've asked you for your phone number or zip code. It's a strange question, if you don't know the purpose, so maybe you've wondered why. There are a couple of very good reasons for it, and none of them have anything to do with an invasion of your privacy.The zip-code question is purely geographical. The numbers are used to show where all the customers live, so that when it comes time to close stores, or open new ones, they know where their customers live. You might get a new store closer to home, and your local one may close if you routinely drive to the further one.
The telephone number question means that, if you want to return an item, and you've lost your receipt, they can pull up the transaction by your telephone number and honor the return. This can also help make lists of buying patterns to facilitate new sales programs and consider different promotions.