> When a hard drive is retired, authorized individuals verify that the disk is erased by overwriting the drive with zeros and performing a multi-step verification process to ensure the drive contains no data.
Thanks. I guess the reason is to avoid future decryption due to either a new crypto attack or to avoid being vulnerable to potential errors in key generation.
For example, although drives in Google Cloud are encrypted at rest, once they are decommissioned the drives are physically destroyed: https://cloud.google.com/security/deletion/#ensuring_safe_an...