off topic : on the other side, i think is inevitable that at some point in the future players will have AI assistants looking at their screens , making decisions and inputs just like a real human, (heck! you can sort of do that now with linux/x11 , screen grab and proton very easily), i personally would love to see competitive gaming involving AI agents and assistance.
Chess is already there. It's really easy to cheat. You can though analyze games after the fact and pretty reliably conclude whether somebody cheated. That's one example of server-side cheating mitigation. No matter what the client feeds you, cheaters are detected and eventually banned.
(I won't start discussing the merits of copyleft itself, if that's what your "why do you care?" question was aiming at.)