Even in the examples you mentioned I strongly believe one shouldn't mess with their devices. You can just take away their phones. My point is that they paid for

Even in the examples you mentioned I strongly believe one shouldn't mess with their devices. You can just take away their phones. My point is that they paid for the device so they get to use it however they want to. Whether they could use it or not depends on the setting they're in, not on whoever "sold" them the device.