Point 1: Most of WGT's revenue is is based on advertising. It is in their best interests to never close accounts. By keeping all of their accounts open they can give inflated numbers to potential advertisers about how many people will see advertising. Just scanning the list of WGT players it quickly becomes evident that many accounts are held by non-playing Hacks and Amateurs who are at very low levels.
Point 2: The backdoor to Oakmont has been nailed shut.