sudoers do not automatically have access as root. They have access as the configured user. It is possible and correct to provide users access to run tools as other non-root usres.
Any users who have access to run a shell or a command that can give shell access should be the users you would trust with the root password. With sudo it is possible to run a system without a root password. All uses of sudo is logged, which is not the case with commands run as root.
As noted it is possble to limit access to specific comands. The example sudoers has a number of command sets you might want to grant to specific users who need to do task requiring root privileges. By using sudo it is possible to allow this without giving them the root password.
Anyone who can run a script or command with root privleges, which they can change has effectively been given root access. You need to trust these people, or don't give them the access.
There are a large number of task which require root access. With sudo you can safely delegate these task to backup operators, webmasters, etc.
Sudo is far more secure that the alternatives. If misconfigured, or if incorrect access is given to untrusted users it is a security risk (hole).