Earlier quoted context omitted.
LLMs don't have a concept of sources for their statements. Ask them to give you some literature recommendations on something it has explained to you. You'll get plenty of plausible sounding papers that don't exist. Humans know to some extent why they know (read it in a text book, colleague mentioned it). LLMs don't seem to.
Ask a human to provide accurate citations for any random thing they know and they won't be able to do a good job either. They'd probably have to search to find it, even if they know they got it from a document originally and have some clear memory of what it said.
I can’t tell you the date of every time I clip my toenails, but if I had to could remember it.