It makes a lot of sense from a technical perspective.
It doesn’t really have any more access than any other game you’ve installed with admin righta. The only difference is requiring it on startup, which helps prevent it from being circumvented.
We may see a day where you can’t have games and personal stuff on the same OS. Hell, with the recent Steam issue, you could say we’re there now. But if that does happen, it won’t be because of Riot.