Comment by fluoridation
4 hours ago
A lot of games have tacked-on online features to excuse the existence of the server to enable DRM, and a lot of multiplayer games arbitrarily don't offer a way for clients to double as local servers like in the heyday of arena shooters.
Sure, but the existence of such annoying things does not mean that's the only reason to use a client-server architecture and that it would only affect those games.
It's not the only reason, but that does cover the vast majority of online-required games.