Valve has introduced new rules to ban games that require players to watch in-game ads to play. The company prohibits cross-promotion and product placement, but allows for other forms of advertising. Developers must remove ad-based business models, such as requiring players to watch ads or gating gameplay behind them.
Some alternatives include switching to a single purchase model, making the game free with optional upgrades, or removing ads from platforms used on Steam. Valve also disallows charging other developers for access to its features, including sale pages and storefronts.
This move aims to clarify what is supported on Steam, as some games may use similar tactics to those found in mobile games. A new feature warning users about update frequency has also been implemented, providing more transparency and trust for players.
Source: https://www.eurogamer.net/valve-bans-all-steam-games-that-force-players-to-watch-advertisements