Because there are problems out there that you're not going to feasibly solve on your own.

Think of it this way: do you ever look up anything on the internet? If yes - why did you do that, when you could just find out the information yourself by working from first principles? Likely not only because it's orders of magnitude faster, but because doing it yourself would probably result in significantly lower quality thank just looking it up on Wikipedia.

LLMs are like search engines on steroids. They really can help you explore problems that have already been described in the literature, so to speak.

But of course that changes how our brains need to be wired. And it's not necessarily bad. When I was growing up, the adults were really worried that the use of search engines would degrade the ability of children to look things up in the library. And they're right - I would indeed have a more difficult time going to the library, finding the right shelf, finding the right book, looking through the index, and scanning the pages for the information I was looking for - because that's a skill that I haven't practiced because I could just do a web search for the better part of my life. Doing a web search is a different skill.

That's not to say that this is all fine and just a technological development like any other. I think we do need to be careful about how we use LLMs and when, especially in order to think through problems ourselves. I think that we were already over-reliant on the Internet before LLMs came on the scene, and it will likely get worse now. But the reason that they're dangerous is because they are in fact really useful tools too.