It's because there's effectively a class-action suit going on right now, but because the user agreement says you have to use arbitration, there were tens of thousands of people who are like "sure let's go to arbitration". Valve is losing tons of money having to fight all the suits.
I'm not a lawyer so I have no clue about the legal issues, but I'm more than happy to put my name to anything that costs a corporation money. I don't even need the money. They can take it out of Valve's pocket and burn it for all I care.
This is a laughable suit. Why do you feel entitled to any kind of compensation over what Valve takes before paying developers as a consumer? If games on Steam were 30% more than games anywhere else, there might be merit to it; but that isn't the case and it's what this CLA is arguing.