At least in case of the kitchen contractor, you can trust all the electrical equipment, plumbing etc. is going to be connected in such a way that disasters won't happen. And if it is not, at least you can sue the contractor.
The problem with LLMs is that it is not only the "irrelevant details" that are hallucinated. It is also "very relevant details" which either make the whole system inconsistent or full of security vulnerabilities.