I think it would be better for casinos too if there were no gambling addicts. If everyone was gambling responsibly, the negative connotation surrounding gambling would disappear and without it online casinos would surely get more customers in the end. After all, their aim is to make profit, not to create problems for people.
I don't think that the negative connotation stops people from gambling or makes new gamblers stay away from it, so that isn't a reason why casinos would want everyone to become responsible gamblers but they would want every gambler to keep spending as much money as they can because they know once the money has entered their bankroll, there is nothing that can take it away from them even if the gambler starts spreading negative news about them.
Casinos, their owners, and the management barely care about gamblers' sentiments or their personal lives. All they care about is their businesses and they are not wrong about that. If I were running a business, I would surely want every customer to come and use my business and products as much as possible since that will bring more revenue for me and my business.