What prevents them from running updater unprivileged and asking for root before installing the update? Or better - why can't it be installed and run under the u

What prevents them from running updater unprivileged and asking for root before installing the update? Or better - why can't it be installed and run under the user. Most other apps are simply copied to Applications and run as the user. I can imagine they want Windows-inspired multi-user install. But still there is no need for running the updater full time with root privileges.