You might not have noticed, but that's also where anti-cheats started. All 3rd party anti-cheats started on community servers because well you aren't getting them into official servers easily. And then game developers saw that and integrated it for the users. Quake 3 even had Punkbuster added at some point for example.

Plenty of modern community servers still do the same. Face-it servers for Counter-Strike 2 will have additional anticheat, not less. Modded Grand Theft Auto V servers, FiveM, built their own anticheat they call adhesive before RockStar ever added anticheat to the full game, and this prevents it from running on Linux to this day.