I don't think it's their information per se, so much as how the LLMs tend to use said information.

LLMs are generally tuned to be expressive and lively. A part of that involves "random" (ie: roll the dice) output based on inputs + training data. (I'm skipping over technical details here for sake of simplicity)

That's what the masses have shown they want - friendly, confident sounding, chat bots, that can give plausible answers that are mostly right, sometimes.

But for certain domains (like med) that shit gets people killed.

TL;DR: they're made for chitchat engagement, not high fidelity expert systems. You have to pay $$$$ to access those.