This is similar to what competitive Counter Strike has become. Even though Valve has been talking about some interesting anit-cheat methods [1], third party matchmaking services rely on such client software to try to combat cheaters [2].
Might be worth noting that one of those third party matchmaking services (ESEA) deployed a bitcoin miner along with their client not that long ago. Caused a huge uproar.
True. Hard to believe that was already 5 years ago, but I think you're right. I was pretty furious at the time. I also seem to remember that ESEA got hit with _super_ heavy fines for way more than they ended up earning in bitcoin. Probably a fairly strong deterrent.