I'd probably have to argue that it's more Steam's issue than SE's. Of course, I don't have any evidence or proof to back this up. But Steam have iffy requirements and never really deliver hard copies or additional physical extras. Outside of their own products, like the Steam Link, controller and VR headset, they're purely a digital media platform. So again, I'd have to believe Steam are being weird with it rather than SE squatting over the Steam playerbase.