The problem is that the credit bureaus can and regularly do make mistakes, or the creditors reporting data to them do, and when $shady_business says someone owe

The problem is that the credit bureaus can and regularly do make mistakes, or the creditors reporting data to them do, and when $shady_business says someone owes him thousands of dollars despite said debt not existing, or when someone steals your identity because the credit bureau has laughable security, the burden of proof is on the accused.