Avoiding gambling in front of my children or any other teenagers is the most crucial rule I follow. if kids witness us gambling, they can be motivated to do the same. In my opinion. due to their youth and immaturity, it could negatively affect their future. Kids always tends to follow their elders. So I don't want my kids to catch up my bad habits.
Another post without any proof. Kid saw you eat broccoli, based on you logic, the kid will also taste and eat it. And become super healthy, as he is eating vegetables of vitamins. But in reality, kid wont eat it, and would rather eat fries or pasta.
All those who say “kid will do everything parents do” either dont have kids, or dont know their kids, or follow some life standarts of elder generetion.
It doesn't necessarily mean that everything we do, our kids will do also. BUT most of the time, they always from what we do, what we say and what we teach them. What negative affect would kids have? You have mentioned that. Please dont say addiction. Be more original. Those who gamble not always are addicted.
I'm not sure if you hate the guy who you are replying with 
even me I can't think of a negative effect on a kid directly if he sees his parents gamble than increased in gambling problem to a kid in the future, but surely there will be a negative effect on that family, more probably financial consequences. If gambling is bad - why you gamble? Why you show bad example for everyone around you? 
There's nothing wrong saying bad examples or bad effects of gambling, because it is true at the end of the day.