Subsidized devices blur the line between a fee for terminating service early, and paying off the cost of the device. Perhaps the former should be banned to encourage competition, and the cost of the device and the service clearly separated. That way it's clear when the device is paid off and (in my imagined ideal regulatory scenario) must be unlocked.
a poor person would have to pay BOTH. An early termination fee AND then go buy a new phone
They probably don't have to pay the fee. They might owe it legally, but the likely consequences for not paying are some impact on their credit score and inability to get service from that carrier under their own name for a while.