Seems you're contradicts yourself.
If you said the environment is full of smokers, then you will become smoker too. But you said it's depend on your personal choice, this mean environment do not always make the adult become smoker even he surrounded full of smokers.
Yes, it depends on your personal choice because if someone has a strong character, he will not be tempted by anything and be able to choose what he thinks is good.
But many people become seduced by their surroundings and in the end, they follow what the people in their environment do.
We decide what we want to be and not depend on the environment.
Children would either copy what they see on their parents or question them, it's their only two choices. If their parents are addicted to gambling, then it would cause chaos into their family that gives children truma, that's why they'll hate their parents addiction forever and will not do the same like their parents. Mostly children who has a worst environment turned out to be a good example to other people, some are worst than their parents.
That's because a child only sees and imitates what his parents do so it makes us as parents be careful when in front of them. We must be able to set a good example so that they see and imitate it for their future provision. If we can set a good example for them, they will surely understand and be able to distinguish what they can and cannot do. This will also prevent their children from doing something bad when they grow up. Children need the understanding to understand things so this is what makes us have to be able to explain everything properly and correctly.