Afaik, except for steam only Itch even has a native Linux client for starters? EGS is a pos software that doesn’t even have an “appear as offline” mode and bleeds money while still taking a 12% cut. And Epic is not a small indie company trying to break into the market.
Steam workshop, their VR integration, their work with Proton for Linux, Steam marketplace, the ease of generating keys for resellers without the 30% cut, great mobile app/interface, actually good storefront browsing, the list just goes on with things Steam does better than any competitor, and that’s just a few examples of where the 30% cut is going (ofc they still make absolute bank on top of this).
But regulating this to something insane like 5% would definitely make us lose out on several of these features, not to speak about future features.