For shared local usage or "pet" (as opposed to cattle) servers I'd agree, and in fact this is close to what Linux was designed for, since I'd consider the multi

For shared local usage or "pet" (as opposed to cattle) servers I'd agree, and in fact this is close to what Linux was designed for, since I'd consider the multiplexing lab server to also be a semi-trusted environment. I'm referring more to how Linux is used in vast pools of "cattle" servers in Cloud, locally by eg one main user (who doesn't need multi-user but probably still needs some notion of "admin" and per-program permissions), or in a corporate setting (where the actual identity system is managed remotely). This is probably >99% of Linux environments.