A market is not a resource. It’s not coal in the ground that Valve came along, dug up, and provides to people for a fee. They built the whole market, it’s theirs, and they built it when there were no guidelines or examples to follow either. If you want your game on there it requires a mutual benefit because if only the game makers benefit then there won’t be a market anymore due to no doubt astronomical costs of servers, development, moderation, etc. If there were no charges there’d be no market and publishers would have to sell their games on the remaining markets which, at the time of Steam’s creation, was nowhere and even now is multiple inferior places.