Exactly why phones NEED to require the passcode/touch ID/whatever when turning the device off. Could add the same to Sim removals: "SIM HAS BEEN REMOVED, ENTER PASSCODE TO DISABLE ALARM"

It presumably isn't impossible to design phones with hardware designed to transmit their identity as soon as connectivity is restored even after the SIM and firmware is replaced, the credible threat of which would be enough to eliminate black markets in that type of mobile phone.

The cynic in me suspects that carriers and OEMs long ago estimated the marketing benefit from an "unstealable" phone to be rather less than the revenue from more marketable overpriced phone insurance and increased replacement rates.