Third parties can be put into two categories. There are those that submit a complaint on behalf of the person who had the negative experience, and there are those who submit complaints based on what they've seen on YouTube or the news, say. Those are two different groups of third parties.
I agree that the first group should be able to submit complaints. However, lawyers sometimes want to bring systemic issues they have observed to our attention, and we listen to what they have to say. It doesn't mean that I'm going to initiate a review, but I am willing to listen. I am also well aware that non-governmental organizations are usually the ones who examine these issues.