It's a setting that iPhones had for a long time, where they would prompt you to join the nearby WiFi networks. I don't currently have one, so I don't know what it's currently like, but a large number of people would pull out their phones, start doing something, dismiss the pop-up, and continue, many times in a day. Probably they almost never actually used it to join a WiFi network at all. You could turn it off in settings but they didn't.