This does not make a lot of sense to me.. I mean, if some user on the client has hacked root, then game over man.
I think the concern is for sites where you don't *have* to hack root - e.g., a network where users are given root privileges on their own workstation. One might not want those users to have *arbitrary* privileges, e.g. the ability to read other peoples' files, just because they have sufficient privileges to configure and administer the machines on their desktops.