Disabling expired, inactive, or otherwise anomalous accounts supports the concepts of least privilege and least functionality, which reduce the attack surface of the system.
Verify the DBMS is configured to disable accounts when the accounts are no longer associated to a user. If the DBMS is not configured to disable accounts when the accounts are no longer associated to a user, this is a finding.
Configure the DBMS to disable accounts when the accounts are no longer associated to a user.