Apple ID primary email
Apple needs to enable a way to remove accounts that have been created accidentally and tied to your apple id, or a way to transfer your subscriptions of apple care to new one this is ridiculous.
You can log into your cloud account for the old ID, and remove aliases in icloud Mail.
You can manage your subscriptions there.
Apple Care follows a device, so you can cancel Apple Care, but it's not transferrable. Buy a new device, buy Apple Care again (think of it like a warranty - you buy it for your TV, and when you buy a new TV, the warranty doesn't transfer).
It's a bit of housekeeping. But it's for good security reasons.
