They are invited to membership based on good business practices . The biggest plus for arbitration vs court is if the arbitrator needs to see what the problem is the arbitration can be held at the point of dispute. No judge will ever go to a customers home. If the dispute is around a job at the home the arbitration will be held there giving both parties the opportunity to point out the problems or correction of problems to the arbitrator. Is must fairer in this sense that court.
Court can take months or possible years to resolve an issue where arbitration can be much sooner.
It is binding on both parties.