There are plenty of ways to tether devices to a phone. Doesn't matter if your provider doesn't want you to do it or not. USB cable, Bluetooth and even WiFi. My phone, using the now obsolete WebOS has a tethering program I downloaded and installed that basically takes over the WiFi allowing multiple devices to connect to it at will (via WiFi). For Android users there are a multitude of ways to do it depending on what skill level the user is (i.e. basic programs vs. rooted programs). So when cell providers don't want you to do something, it just encourages users to find other ways to do it