Because gambling isn't just a game anymore; it's a dynamic industry and most of the time, it has negative-sum effect on its people. "Dirty" by means of the money you can get from the gambling is from the loss of many, is subjective and cultural view of the matter. These difference in views and cultural perspective divides the role of gambling as entertainment and as way of living. Though there are also people nowadays who consider gambling as both for entertainment and income generating activity. But in the end, money is still money.