Once another party is involved you end up coming up with another agreement and first you need to agree which arbiter is used. You have more choice but where's body that makes sure everybody chooses the better judge so that bad judges get nothing to rule?
You sign up for a law firm and trust it with its choice of arbiters. Much like when you buy a cake, you trust the baker with ingredients and recipes. If you later feel sick, you never go to that bakery again and trash its reputation.
