Apple uses an Apple ID across its whole ecosystem to identify you for syncing, purchases, and more. What happens when you sell or give away a Mac and think you’ve wiped all traces of your identity, but the Mac keeps prompting the new user or owner with your Apple ID account email and asking for its password?
If that’s happening, it’s likely you or the new possessor didn’t wipe the machine completely. I recommend that you perform a complete wipe when handing off a computer.
You can then use a Time Machine or clone of the drive to restore purchases that you are transferring the licenses for along with the machine, software that is free to use without a license or doesn’t require a transfer, and any documents, photos, and other files you’re including.
