The incentives to cheat in a professional competition are more obvious since the money you earn is related to your performance.

In the case of AoC, the only objective incentive I can think about is impressing a recruiter. Maybe it's enough if you're motivated enough.

Why do people cheat in video games?

Good point.

I play chess and some players end up thinking that cheating allows them to reach their real level and that it's just bad luck or conspiracy that prevent them to get to that level without resorting to cheating. Talk about cognitive dissonance.

Money. Being really good at a game can be a source of income for E-sports or streaming.

Online games have always been rife with cheats.