Pay-to-win isn't really the issue so much as microtransactions in general. Most of these games have an in-game currency to buy stuff (some is pay-to-win, most are cosmetics) and protecting that currency (and the virtual goods traded on the market it drives) is paramount. These games also tend to have moved away from 'community hosted' servers, since these give an opportunity for hosters to hack in features that might be detrimental to sanctioned behavior.

In short, we typically see KLA on games with in-game currencies whose servers are controlled by the vendors.

Inasmuch as KLA is actually used as anti-cheat software, it's usually a proxy for actual moderation (i.e. labor). Community-hosted servers generally develop their own processes and customs for handling bad actors, but vendors generally don't want to hand that kind of power to internet strangers.