Valve have updated the developer guidelines for releasing a game on Steam, making it clear that the scourge of mobile gaming advertising-based business models are not going to work on Steam.
I think what matters more, or perhaps at least in Valve’s perspective, is that microtransactions are inherently binding between the game’s developer/publisher and the player, so the game’s developer/publisher is the sole party held accountable here (by Valve), while ads inherently involve and invite a 3rd party advertiser, muddying the situation for everybody. While on the other hand, microtransactions can only be done for content already a part of the game, while ads serve content outside the scope of the game.
So this is much much more enforceable for Valve, while DLC and microtransactions marketing is already subject to the established rules on Steam.
I think what matters more, or perhaps at least in Valve’s perspective, is that microtransactions are inherently binding between the game’s developer/publisher and the player, so the game’s developer/publisher is the sole party held accountable here (by Valve), while ads inherently involve and invite a 3rd party advertiser, muddying the situation for everybody. While on the other hand, microtransactions can only be done for content already a part of the game, while ads serve content outside the scope of the game.
So this is much much more enforceable for Valve, while DLC and microtransactions marketing is already subject to the established rules on Steam.