They will obviously attract people to use the gambling feature of their exchange in order to add more profits aside from the fees that they keep collecting from each traders who uses the service w while in the other side promoting the gambling function will allow them to be more profitable as gambler will always be a gambler. People's emotions have a very high influence with their movements.
Maybe some of their users are gamblers. If the users using another gambling website, tx fee will eat their money, or about minimal withdrawal will make other issues also.