If they are both able to earn their own money, I think they can both continue to gamble. They can also share household expenses. I think there is a possibility that both of them might get out of control, but it is not a sure thing, and both of them can manage to act responsibly. I don't think it's right to have prejudiced thoughts against this imaginary couple. 
There’s no point in even thinking about the fact that sooner or later their joint activities will get out of control. And I hope you understand perfectly well that the consequences for both will be incredibly sad. Not only will they lose all their money, but they will also go into debt that they will not be able to pay off due to their gambling addiction. I went through this myself and I never want to go back to it. I had a very hard time getting out of debt.