Assuming your website is 100% secure is not a good idea. You never know when a vulnerability may be discovered, even in website frameworks that have an excellent reputation for good security.
The majority of restores that we do are for sites that were damaged by automatic updates (particularly with WordPress), manual updates by developers that went wrong, or inadvertent admin changes. Often these actions only require a partial restore, although for a website that rarely changes much, a full restore might be quicker.