When making decisions like this, one should consider not just the desired consequences of the policy, but the difficulty in actually implementing it. Alcohol and narcotics prohibitions fall short here.

It's hard to fully prohibit gambling (because you can play poker around a table, and it's better if that's legalized). It's much easier to prohibit banks from interacting with casinos and TV networks from letting them advertise, as those are large businesses who want to be compliant. That doesn't make gambling itself illegal, but cuts off most of its oxygen.