bulbous-or

I'm not a game programmer. Why do games like VRChat and Fortnite need to use client-side mod detection at all?

If everything goes through their servers, it seems like a huge waste of time. If it's peer-to-peer it makes sense.

I'm trying to google it and there seems to be a lot of semi-informed lore, some people say it's centralized and some people say parts are p2p.