It’s another slice of Swiss cheese. If the user has a strong enough password or other authentication method through PAM, it might stop or hinder an attacker who might only have a compromised private key, for example. If multiple users have access to the same server and one of them is compromised, the account can be disabled without completely crippling the system.

Using sudo can also help you avoid mistakes (like accidentally rebooting a production server) by restricting which commands are available to the user.