I have the same questions as MJBunce, If you win a game of chess while cheating how would you feel joy winning? There is no cash prize or any prize at all. There is only a rank that you will loose if you get it unfairly. If you try to get better at chess then what I do it play bots with 3 crowns then move up to the next. The only prize you get from cheating is dishonesty.
Well, since 3 people asked this, I'll try to answer.
Cheaters don't win, because as you said they weren't the ones playing the game... but think of it this way, they don't lose either. Losing is unpleasant, and they avoided it.
They can also fool people into thinking they've won. Obviously this is fake, but unfounded admiration from others can be more pleasant than none at all.
Also a cheater may be upset about something bad that happened to them, so they want to go online and hope to cause someone else to suffer. Sometimes the world is chaotic and cruel, and being the one who administers the cruelty lets the person be in control which is a nice break from the way they feel their day to day life usually goes.
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I mean, that's overthinking it a bit. Most cheaters are kids. So they could be doing it out of curiosity as much as anything. Kids learn about the world by experimenting with boundaries and observing the consequences.
People just want to win which is the problem. The engines are accesible and the best solution Then would be if for a player rated like idk, 2300 and plays a 99.0 accuracy game he must be cheating because sure, he is high rated but that accuracy is WAY TOO high for a 2300 or if the person does many top engine moves without a single inaccuracy or good move then it's definitely that it's cheating.