I'll be as quick as I can be.
It's the articulation of the complaint, which is not something a firm-focused provider will be interested in doing. It's the ability to do the investigation, not simply accept the paper file submitted by the firm to the dispute resolver. It's the ability to have someone who is actually motivated to do what is fair and independent and impartial between both parties, without being potentially conflicted by where the rent cheque and the payroll are going to come from next.
Finally, I think it's to be a source of that information and intelligence for the government itself, for regulators, to guide good public policy for the future. It's better to prevent problems than fix them.