I get it for Linux and Windows (though I don’t know how MacOS does it) my context here (which I should have been more explicit about) is “ordinary user is installing a closed source commercial large game” (with its own installer) and doesn’t know if they are also getting a free rootkit.
Sure when it’s something you compile yourself and you have some knowledge you can ./configure it to go under your home directory and not need sudo to make install later, but a game with a script or binary you need to run is likely to ask for root on launch (Especially on Windows) and maybe asks later or has command line options for a single user install, but we can assume the user does whatever is default.