Why do we need that for photo, video and audio? If it's about the general public believing something false, they're not going to check the watermarks of random

Why do we need that for photo, video and audio? If it's about the general public believing something false, they're not going to check the watermarks of random internet content or trust anyone who says they checked it. If they really want to know, they can go to the source and if they trust that person or organization, they can also trust the content they published. If it's about use in court, we already have a system for that - the person who recorded it appears in court as a witness and promises that they didn't alter it then if it turns out they did, they can go to prison.