What do we really need LLMs for that humans can't?

I would argue that it's not about whether or not we need something that humans can already do, it's that we don't want a human to do those things because a machine might be able to do it better, faster, cheaper, etc.

A human can operate a lathe, I used to do it, but the CNC lathe I also operated could do any thing I could do much, much faster with just as much accuracy.