Of course everything a company does is in the best interest of the company.

That is not true, but that is part of the problem and also why Steam is at least a little better for us customers. Most companies only do what is good for the stakeholders short term, Valve does what is good for the company/single owner long term. And happy customers are good long-term, but not so important short-term.

It is still capitalim, and thus still terrible. But a tiny bit less terrible.

This will play into it. But Valve allows stuff that cuts into their immediate profits, like e.g. third party sales. I think ensuring market dominance by ensuring customer satisfaction is the more important part of the decision. Steam is imo meant to stay a quality product with a reliable turnover. They are not aiming to become a bookmaker, like the play store or apple store basically are nowadays.