Steam is building support for season passes into its platform and setting up rules to help protect buyers from buying ones with unclear promises. Steam published new guidelines urging developers to “think about whether there’s a customer benefit” for purchasing season passes, as reported by SteamDB creator Pavel Djundik.

You shouldn’t pre-order games, but people do it all the time anyway. Increasingly, people have gotten in the habit of pre-ordering DLC too, paying up front for content that won’t be delivered for months or even years,

Valve has updated Steam's Season Pass policy to make it clear that developers selling one must "clearly communicate" what the DLC is and when it's coming.