Children often try to imitate their parents in many ways. This also applies to addictions. Even if parents tell their child how bad it is to smoke, but they themselves do it, the child is very likely to smoke too. The same applies to gambling. If you do not want your child to do something certain, then do not do it in front of your child.
That because basically child will see from different perspective, they children will think that what their parents do is fun so it is natural for children to often imitate what their parents do.
Basically, logically this is kind of direction and learning, children naturally have fairly high curiosity and they try to try some new things that of course have never been done before.
Parents and people around them will play very important role in things like this, if want children with good development and are able to avoid all bad things, then it is the parents obligation to protect the child environment and also their views on all these bad things.
Sometimes there are some parents who don't really care about this kind of thing, they consider it normal and continue to do everything without any restrictions on their own children.
I believe that restrictions for a person of absolutely any age are very important. We all know what the abuse of sweets, gambling, alcohol, even sports leads to. Everything needs to be in moderation, otherwise over time it leads to problems.
If parents do not limit their children in a reasonable measure, then most likely such children are prone to selfishness, and this will affect not only the future life of the child, but also his environment - primarily his parents.