Betting houses are businesses and, of course, want to make money. But when a customer becomes addicted, they eventually stop betting because they no longer have money to spend. In other words, they stop being profitable for the house. Furthermore, no business wants to be known as a place full of addicts; this damages its reputation and, ultimately, drives away other customers. That's my opinion.
I'm not sure those who are addicted will simply quit gambling. I think if they're addicted and run out of capital, they'll likely try to find money, most likely to gamble again Unless the addict realizes it and wants to recover from their addiction they won't be profitable for the casino anymore. However even then the casino won't suffer any losses because there's more than one person gambling. I think the casino still profits from people who gamble even if they aren't addicted.