If you make a ridiculous argument using confabulated case law as a lawyer, you can be subject to discipline by the state bar and even lose your law license. The legal system's time and attention is not free and unlimited and that's why you need a license to practice law. The judges and so forth don't want to deal with a bunch of people talking nonsense. Who is the lawyer who is putting their reputation on the line for the AI's argument? The people doing this want to say nobody is at fault for the obviously bogus arguments it's going to spout. That's why it's unacceptable.