Because we're not even close to that happening. However I've observed a sort of cognitive decline in a few formerly experienced and extremely knowledgeable developers whom I used to respect. They happen to be the most vocal supporters of LLMs now and sometimes our discussions get so ridiculous I have to practically beg them to put the LLM down and just think about what they're saying for just 5 seconds. I think they're about a year away from believing that the sky is green if the AI says so.

So maybe LLMs will win on a technicality by making us more stupid as a species.