When we deleted a security principal that had a role assignment, the security principal will be listed as Identity not found and an Unknown type. Even if it doesn't a problem to leave those role assignments where the security principal has been deleted, but it was not used anymore and no longer useful. It also made a mess of space for handling role assignments. So, it would be nice if the service principal and role assignment will be deleted together to reduces the number of manual processes and saves more time.