A lot of this, I suspect, on the basis of having worked on a supervised fine-tuning project for one of the largest companies in this space, is that providers have invested a lot of money in fine-tuning datasets that sound this way.
On the project I did work on, reviewers were not allowed to e.g. answer that they didn't know - they had to provide an answer to every prompt provided. And so when auditing responses, a lot of difficult questions had "confidently wrong" answers because the reviewer tried and failed, or all kinds of evasive workarounds because they knew they couldn't answer.
Presumbly these providers will eventually understand (hopefully already has - this was a year ago) that they also need to train the models to understand when the correct answer is "I don't know", or "I'm not sure. I think maybe X, but ..."
Its not the training/tuning, its pretty much the nature of llms. The whole idea is to give a best quess of the token. The more complex dynamics behind the meaning of the words and how those words relate to real world concepts isn't learned.