Because there's always an unfound backdoor that can be exploited. Pubg is a great example of this. Battleye was intended to find any such cheats and shut you down if you tried to cheat by introducing code, changing values etc. Unfortunately, it's software and as such has limits. It's limit was found by the sheer amount of avaible cheats, so Battleye got stricter and stricter until it reached a point where even a slight isp glitch or slowdown or brown-out in speeds was seen as an attempt to hack/cheat. Forums are full of ppl complaining that they were happily gaming and 'bam' kicked and banned for no reason other than isp slowdowns, their AV kicked in, windows updated, other other stupid reason that had nothing to do with the game.
There comes a time when ppl need to take responsibility for their own actions, it's a game, to be played. It's not a contest to be won by cheating your way through. Nor is it the manufacturers/hosts responsibility to police your actions. You should police your own. If ppl played the game as intended it be played, non of this would be happening, but there's always 1 bad apple somewhere. This time, the cheater author was nailed, and no matter the actual amount, he took money away from the company. Legally, that's called Theft. And the Judge nailed him for it.
Go Judge.