Because it’s a cat-and-mouse game. Bot makers find a new way to go under the radar, game developers have to find a way to patch that and detect it. The process continues and it’s probably automated… because doing things by hand in IT is not sustainable.
You also don’t want it to be blatantly obvious what you just did to detect the bots. Therefore, they might wait a little before making changes and wiping out all the bots.
Exploits happen in the same fashion. If the exploiters know exactly what you just patched, they’re already a step ahead because they’re thinking about how what they changed may be patched… so if it’s obvious, they already know exactly how to fix their exploit and keep doing it, just in a slightly different way. It happens all the time.
Versus buying gold it’s blatantly obvious. There’s no memory injection. There’s no programs running outside of the game. There’s just gold going from one character to another.
What’s difficult to understand about the difference between software manipulation and sending gold? They’re two very different things.