:O
And what about the Sony tax? And the Gog tax? And but Windows store tax? And the Nintendo tax? And the Apple tax?
Why the outsized negative framing of one company? That's the subtext of this article. This is exactly what it's talking about.
I can't tell if you're being intentionally obtuse over the difference between an open and closed platform. For consoles and Apple devices, which are closed platforms by virtue of controlling both the hardware and software, there is no competition for delivery mechanisms, and hence no room for discussion.
On Android—guess what, there is room. That's why Fortnite isn't offered on the Play store—you have to download the APK directly. It's why large entities like Amazon have tried run their own software ecosystems on Android, yet can't afford to do so on iOS. In China, there's a litany of competing app stores because Google is banned and doesn't have hegemony over the ecosystem.
If you want to talk about GOG and other PC storefronts, their cut is based on the industry precedent—in this case, a precedent mostly reinforced by Steam. But then again, these smaller storefronts aren't particularly good at courting patrons, and at their scale, it's questionable whether they're even sustainable businesses, which is why they're mostly either dead, about to die, or perpetually unable to grow.
"Why the negative framing of Steam" is an obvious answer. Epic isn't in a position to negotiate the cut on closed platforms. They strike where they're able to. And despite Android being a semi-open platform, it's still a risky endeavor to run your own store (again, see Amazon). Epic wanted to diversify in the face of decreasing Fortnite revenue YoY, saw PCDD as a market rife for disruption, and swung for gold.
Also just going to add that you shouldn't be forced to question the state of the industry standard if you just want a better cut on PC. It's not Epic's responsibility, or any other single dev or publisher.