That seems like an uncharitable take. It is entirely possible to re-sell a modern phone, and this happens quite often. Before selling the previous owner must sign out of the device's cloud account and perform a factory reset.

Differentiating between the intentional re-selling of the device, and the selling of a stolen device does seem like a tricky problem, and personally I think this solution seems reasonable. If the device manufacturers are at fault of something it would be poor UX for not making this more clear, otherwise I believe these companies are acting honestly here.

Why can't they implement a second factor of auth to determine the phone's real owner? Or is that deliberately avoided to prevent victims of theft being put under duress?

I mean, we have that. It's called an imei and you can't change it.

All that would be needed is for anyone selling a phone to provide the imei and some id to a govt service to assert that they are the current owner and intend to sell it for x price on y day. If you don't do this check and buy a phone, you're held liable if it is stolen. If you do, and it passes but later turns out to be stolen, automatically reimburse the buyer when you return it to the owner and make the seller liable to cover all associated costs in addition to the handling stolen property.

Most of this is already implemented for cars via vin, and doesn't require that an unelected central power has carte blanche to do whatever they want to it at any time.

You can't change it, but you can find it inside the phone, no?

That's...the point?

Have a central database of registered owners.

Allow current owner to assert that they own a given imei in a way that the buyer can check on said database.

Register the transfer of ownership during sale.