That's a good question. I know I am. Perhaps it's because they are innocuous, fixed unit devices. Perhaps it's because they were "sold" to us a long time ago as shoplifting deterrents, before AI, the interwebs, cloud storage of your underwear size. Maybe most people just don't take note of them. Don't know. Nevertheless, I think if you asked, most people would say that they don't like being watched.
A robot, or scanner, moving among us is a real "in your face" act. Maybe that makes it worse in my mind.