Well spitball a bit harder because it's actually a hard problem to solve - given buying and selling of used items, how do you prove who actually owns a device? The official registered owner is the one who's iCloud locked the device. If you were the legitimate owner, you could just iCloud unlock the device. If you bought it off Craigslist legitimately, the old owner would be able to iCloud unlock the device, if cooperative. If it's a time-based thing, then thieves just have to steal the phone, wait 6-months 3-years whatever, and then they get a free phone/laptop/iMac. If you have to show a receipt to Apple to prove you bought it, a thief could just have a friend make a post on craigslist that they "answer", and there you go.

If you go into the Apple store and request a firmware reset, Apple will ask you for the original receipt before sending it off to the factory to do it, but they can. But given how expensive their laptops are, a rogue employee at a computer recycling center could still slip in a few stolen ones and pocket the gains if Apple worked with recycling centers to unlock their laptops.