Because verifying that answer would take more work, then researching and answering it yourself.
Not necessarily, again it depends on whether it's right or wrong. If it's right it can give you a lead to research into, if it's wrong then you're just wasting your time following a dead end.
You can also just ask the AI to give it's sources. If the AI is agentic and not just a simple LLM then it is already probably doing a web search and "reading" articles and papers on the topic to synthesize the answer, if it doesn't give those links with the output you can usually just ask it and it will embed them in the output, making the verification part easier as you can just read them yourself.
that the discussion devolved ....
Yeah but it seems OP was the one that devolved it. They could've just said that they think the AI is wrong for x reasons and continued the discussion but instead they made up a fake model with a fake answer which inevitably leads to a discussion of the different models contradicting each other and why that is. And again this is for a contradiction that probably doesn't exist.
This would be like if someone said their doctor told them to do something and I lied and said my doctor told me to do the opposite and the discussion turned to which doctor was more trustworthy. Then saying that even though I lied, the fact that we wasted our time discussing the trustworthiness of doctors means we shouldn't consult them at all as it takes too much time arguing over my made up scenarios.