Previously if you had a dispute with Steam you would go to a mediator appointed Valve and you discuss things with Valve and come to an agreement. Sounds good, as it doesn't mean you have to involve lawyers.
Until you realise, Valve is paying for the mediator so the mediator has an incentive to agree with Valve to keep the business. In addition, any agreement is purely between you and Valve. It effects no one else, any previous agreement between Valve and the previous person has no bearing.

Contrast that to going to court, court decisions are binding and are able to be used in other court proceedings.