Because intentionally fucking over their customers would be an impossible secret to keep, and when it inevitably leaks would trigger severe backlash, if not investigations for fraud. The game theoretic model you’re positing only really makes sense if there’s only one iteration of the game, which isn’t the case.
That is unfortunately not true. It's pretty easy to mess with your customers when your whole product is as opaque as LLMs. I mean they don't even understand how they work internally.
