California judge Thomas Hixon says that Valve must comply with a subpoena from Apple in their legal fight with Epic Games. Apple subpoenaed Valve because they feel certain Steam information will be important in their case that they are building against Epic. Valve claims that Apple's case is all about mobile and their data has no bearing on this case. They also say that Apple is using this only to obtain a bunch of third-party information.
Epic alleges that Apple's app store and its mandatory 30% cut taken from all sales is anti-competitive. Apple wants the data from Steam to help show that there is still a bigger market available for games like Fortnite to show that Apple doesn't have a monopoly. Apple wants the information on 436 games available through Steam, along with sales data.
(The subpoena) "seeks information relevant to the effects of competition. Recall that in these related cases, Plaintiffs allege that Apple’s 30% commission on sales through its App Store is anti-competitive and that allowing iOS apps to be sold through other stores would force Apple to reduce its commission to a more competitive level. Well, Steam is one of the largest video game stores for PCs, and it too charges a 30% commission."
Judge Hixson didn't give a crap about any of that and sided with Apple. He said that Apple had "salted the earth with subpoenas" and told Valve "don't worry, it's not just you."
This is just the latest in the ongoing legal fight between Apple and Epic.
Besides, Valve already share information that would be enough for most people.