WGT knows and quietly allows it to go on for financial reasons. Not only those extra accounts in use provide additional revenue through equipment charges and gambling commissions, they are able to count each one as an additional potential customer when they are selling advertising. The more accounts, the more they can charge.
They will shut down an account from time to time when a fellow member turns someone in to give the appearance they are doing something about it. In reality I don't think they're very interested in putting much effort into shutting them down.