I thought the point of the thread was to show how misleading Tim Sweeney is when he says he doesn't know why Valve takes such a large cut. As well as to the people here that then parrot the same thing.While interesting, the thread title and overall conclusion are a bit misleading. Steam's cut from the storefront (which is what everyone compares with Epic's 12%) is still 30%, regardless of if they are offering the perk of free key generation.
My takeway was that if Valve was to lower or match the EGS's 88/12 cut they would no longer be able to allow for free key generation because of how many copies are sold on those sites. They would then have to charge customers payment processing fees, and finally, they would no longer be able to afford to sell the Steam Wallet retail cards that allow people to buy games without a credit card or similar online process.
So when Sweeney says he doesn't understand why Valve takes the cut they do he is either uninformed or just doesn't care about passing on fees to the customers to save publishers money.