[UseStrict]

Apple could just unpair parts when the phone itself is reset/deactivated. And new genuine Apple parts could at least have a one-time automatic pairing when signing in with your Apple ID.

Stolen phone? The phone is still activated, part can't pair with new phone. Not perfect, but at least somewhat less anti-consumer.

[londons_explore]

But if that were the case, there would be plenty of people willing to sell you a refurbished screen for your 2 year old iphone for $100.

By restricting the reuse of parts, when you crack the screen of your old phone, you are faced with a $500 repair bill, and decide to just pay your phone company $50/month for a new contract that comes with a new phone.