I think first, we need to look into what su and sudo actually are

su - stands for Substitute User. You use this to switch to a shell as another user using that user's password. Commonly used with root. Does not require a password when executed as root.

sudo - allows a permitted user to execute a specified command as another user. Also commonly used with root. However, this allows you to specifically manage what commands may be executed as another use. (For instance, you could give a user the ability to run an init.d script but nothing else.)

Note, you can always run sudo su or sudo -i and that will give you a root shell. However, no root password means no logging in directly as root... which means no one can break into that user.

I think first, we need to look into what su and sudo actually are

su - stands for Substitute User. You use this to switch to a shell as another user using that user's password. Commonly used with root. Does not require a password when executed as root.

sudo - allows a permitted user to execute a specified command as another user. Also commonly used with root. However, this allows you to specifically manage what commands may be executed as another use. (For instance, you could give a user the ability to run an init.d script but nothing else.)

Note, you can always run sudo su or sudo -i and that will give you a root shell. However, no root password means no logging in directly as root... which means no one can break into that user.

EDIT: so maybe this answer your looking for is: not having a root password forces you to use sudo, which in turn naturally aligns you with the sudo philosophy which suggests you to enforce greater control over the actions run as root.