Machines can’t be held accountable, which is problematic in law particularly.
The point is that you expend a lot of effort into the engineering problem that is ensuring, to the absolute best of your ability, that what the AI gives you back is correct. Then the humans still verify it. One could then ask whether that doesn't just make the whole automation process redundant, but I don't think so. There are ways to make the verification process much easier. For example, direct links to and quotes from every cited thing, and so on.