Okay Dopp. I want you to picture this. You are an administrator for steam, and your job is to deal with a bunch of minors, who don't know how to handle the english language, let alone their own money.
Now do you possibly see why A. Nobody wants to fucking do this. B. It's a waste of resources to govern something that should not be governed. C. It is absolutely impossible to govern this efficiently without enforcing trading without money or having some kind of paypal thing through steam, at which point there likely would not be a reason to even have this team.