For one thing, it's not actually that useful to have such a person at your fingertips. You put up with the drain a junior places upon you because with training, he'll be able to come into his own and pay off the time invested. An LLM can't do that. Also, a lot of people incorrectly believe that an LLM is smarter than a new grad, and of course the companies making them have a vested financial interest in lying to you that their products are smarter than they are.
