I’ll assume since I am someone else, but kernel level anti-cheat is basically Spyware, or at least a privacy concern.

Yep, the other two commenters summed it up well: I’d rather not have software for a game that I play running and phoning home every time I boot my computer (in other words, a rootkit). I also am a Linux user, so they just don’t work for me.

Could also be that they are playing on Linux. Kernel level anti-cheat doesn’t work there.