I’m still playing Diablo II

Epic Games also takes 5% of all games that use the Unreal engine, unless you use the Epic store.

they explicitly do give out keys for resale. Steam Keys are a free service we provide to developers as a convenient tool to help you sell your game on other stores and at retail

they say on the platform that exploded because Reddit decided to Spez.

Also developers can generate a unlimited number of Steam keys for their games that they can sell on other platforms and steam doesn’t take any money for. So you can make MyCoolGame throw it on Steam then sell copies of your game on MyCoolGame.com give your customers Steam keys and keep the whole price while still benefiting from Valve’s infrastructure to support downloads, friend lists, updates ect.