And yet there are plenty of action games that remain fun to play while running on platforms that ain't locked down tighter than a jelly donut stash in a weight loss clinic. Botting and aimhacking do happen, but apparently not with sufficient frequency to be a problem.
Quite a few games do use kernel-mode anti-cheat, but it's far from "most" even in the narrow category of multiplayer first-person shooters, let alone multiplayer games in general.
Large studios are installing anti-cheat rootkits for the same reason they used to install anti-piracy rootkits: because they're excessively paranoid about any possibility whatsoever of revenue loss. Anti-piracy rootkits fell out of fashion when enough customers got fed up with them to stop buying games with them; I would be entirely unsurprised if anti-cheat rootkits met the same fate - especially given the recent popularity of devices like the Steam Deck that make shipping such rootkits (for either reason) exceedingly difficult.
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EDIT: and in any case, I'll take "have the choice to install kernel-level anti-cheat on my machine if I so choose" over "not have that choice" any day.
