Im a software engineer and know how to be a software engineer, yet I find LLMs quite helpful. Why should a plumber be any different.

the question was rhetorical. but, since you responded – do you think that there are limits to who can or should use ai? if the plumber's use of ChatGPT improved outcomes, isn't that preferable?

some knowledge is likely "cached" in the plumber. maybe he doesn't ask the same question twice. i'm sympathetic to the plumber, but i think your concerns of erosion of knowledge or skill are worth pushing on further.

Which part of being a plumber? Was the house installed with something non-typical? Would you rather have them take an additional 30 minutes looking up their technical manual?

Without further knowledge of what was going on it's hard to say why they used ChatGPT.