Apple could empower their customers to be good citizens of the earth who want to reduce electronic waste while simultaneously making the lives of thieves difficult.
They likely considered the possibility and decided that it wasn’t worth the extra hassle.
They're not cryptographically registered. iOS does a simple check to see if the serial numbers of the installed parts match the expected original values. Also, you can still sell them, and you would not have a hard time finding a buyer, because they're still intrinsically valuable parts and can still be used (with some annoyances). Anyhow, I'm sure someone will reverse engineer the system well enough to reprogram the serial numbers without Apple's assistance eventually. I can't wait -- the writeup will probably be a fascinating read, and it will provide users more control over their own devices, which is always a good thing. Same reason it made me very happy when it was discovered that Apple dun goofed and let an unpatchable bootrom bug slip into all iPhones from 5S through X, which means these phones are forever jailbreakable: https://checkra.in/
What is the point of stealing an iPhone 13 if you can't just sell the phone on (because of iCloud lock) and you can't chop-shop any of the expensive parts because they're all cryptographically registered?