Steam is an interesting case, because it actually allows others to sell games on their platform -- developers can generate an unlimited number of keys for Steam

Steam is an interesting case, because it actually allows others to sell games on their platform -- developers can generate an unlimited number of keys for Steam, and sell those on third-party key sellers. The biggest limitation that Valve puts in place is that the developer can't undercut the Steam storefront _only when selling those keys_ (ie: if a developer sets up their own storefront that doesn't use Steam keys, they can sell on that storefront without price restrictions). Moving outside of PC games, I think things get very hard to argue for cross-portability. Each platform has a unique (closed-source) tech stack, and that requires paying developers to write code to take advantage of the features available on each of those platforms. Since portability incurs measurable costs, it's hard to argue, for me, that users shouldn't bear some of the brunt of those costs. If legislation were already in place, such a price could be built in to the product.