Chess anti-cheat now relies on looking at your moves and spotting mistakes. Not even grandmasters play tactically perfect games so this works pretty well for finding cheaters. In theory FPS games could do the same to detect aimbotting.
It’s just that it doesn’t work.
In addition, there’s not much these things can do against subtler stuff like ESP.
It is scary how nuanced the cheating tools already here. Here is a video promoting cheat software explaining how nuanced their aimbot system can be made to mimic real play: https://www.youtube.com/watch?v=hrBohlkHMjU