Valve is a very small, very selective company, which rarely produces new products. Despite all the overtures about freedom, there is still a central point of control that can and will put the kibosh on things if they're not going the way they want.
People have a psychological need for authorities. If you don't give them any, they will make their own out of the nearest willing "charismatic" person, who will emerge as a de-facto authority. An explicit structure is better than mob rule.
I don't think anyone believes wealth inequality is not a problem, but I don't think non-hierarchical structures are going to do anything to solve it.
I agree with you, but will the people?
History has shown that people just don't care about doing hard things themselves.
I agree that centralized leadership tends to produce better products, but I don't think a more democratic company would necessarily have to put every decision to vote. Hierarchies could still emerge and responsibility could still be delegated. (Again, see Valve.) But I think distributing power, reward, and responsibility more equally throughout the company would be massively beneficial in terms of "social good".