Riot games use theirs (Vanguard) to improve detection of cheating software. basically the idea is by being on from the moment the computer is booted up it can validate the environment better.

Here's a recent blog post by riot detailing their recent deployment of the system for league of legends, the biggest online multiplayer game in the world

https://www.leagueoflegends.com/en-gb/news/dev/dev-vanguard-...

towards the end it talks about how and why it works