> Plenty of developers sell through the Epic Store (having development funded by Epic), or GOG, or the Humble store, or on Itch.io, or even via microsoft store.
They do, and that's great, but rarely can they afford to not _also_ sell on Steam. Steam will still take their ~30% cut of the vast majority of revenue, still mostly thanks to its first mover advantage, and there's no self-interest-preserving move the developer has against that.
The only exception are exclusives like Epic's, and exclusives aren't exactly great for consumers either.
