Klein had long meetings with S****. They claim it's to benefit all involved but I have no doubt in my mind that they are working for him as well to fight anybody who tries disputing charges on their own.
If you pay them their fees they'll work for you to get the money back, but they are correct that unless you have clear proof that the charges were unauthorized, your stepping into dirty water trying to dispute, and the processing bank will most likely come after you.
Can also be a problem halachilally to dispute. Questions about lying, defrauding/stealing from the bank. AYLOR
The main reason why people aren't suing is bec. it's not a question if this will turn criminal, but a matter of when it'll become criminal. There is too much money, and parties involved here for it not to be.
Once you sue/dispute your connected to the story and subjecting yourself to questions, subpoenas etc.
Although non of the cardholders did anything illegal by swiping/lending their cards to someone else, people might just want to distance themselves from this story as much as they can.