Sometimes users tend to add business emails to their accounts and forget that they do that if they log in after some time.

Having a recovery email address will allow them to find their linked account. The login page could prompt an email to be sent to their recovery email with their login email address.

When updating to a new email address in Settings > Profile, the system could prompt the user if they want to use their old email as a recovery email address in case they need to recover their account for whatever reason.

When trying to recover a password with a recovery email — send the details for the primary login email linked with the recovery email so the user knows which email to sign in with.