Would a decentralized version of Steam do that?

Is that 30% the bulk of Valve’s profit?

What do Indie developers get in exchange for Valve’s 30% cut on Steam that they don’t get elsewhere that charges 30% or charges less of a percentage?

So could physical retailers, so how’s that working out?

I’m not going to say they can’t do that. It’s not a bad suggestion but it seems to be suggested continually in a vacuum without considering other factors.