Well, curiosity kills the cat, as some may say. I doubt that "the rest of the citizens" you're referring to might not engage in finding another loophole to gamble their money.
Same with substance, it's technically illegal, but someone who's super curious might still find ways to test to try something new in their lives.
Now imagine that gambling is allowed and, accordingly, gambling advertising is allowed. How many times will the number of those who decide to try previously banned gambling establishments increase?