To be able to buy and sell goods without anyone besides the person I'm buying and selling from knowing about it. Not because I want to do anything illegal, but for the same reason that you shut the door when you use the bathroom, and don't willingly install cameras pointing at your bed that broadcast to the entire internet. I'm not willing to give up my privacy just so governments can avoid doing the police work they're elected to do in order to prosecute crimes, or so corporations can bombard me with their shitty products.
Whether or not you equate what you do with your wallet with what you do in a bedroom or a bathroom, it's objectively possible to tell what you do in your bedroom or bathroom from what do do with your wallet in many cases. Condoms, birth control, pregnancy tests, pre-natal vitamins, STD tests, gay literature, sex toys, hemorrhoid cream, etc. all are frequently bought without anonymity, but give a great deal of information about what you're doing in your bedroom and bathroom. Maybe you're so "normal" that you've never bought any of these things, or maybe you're in a position where you wouldn't care if those purchases were made public, but if so, you're actually a pretty rare person.
