My dad smoked. Started when he was twelve. But he managed to convince five kids that it was not a good idea. He tried repeatedly to kick the habit but found it too hard. He used to say that the only thing he wouldn't do again if he had his life over again was to smoke. He survived a serious brain operation and then lung cancer killed him. I reckon there must be a few more families where that could happen.
Besides that, there is publicity everywhere about the dangers of smoking. Anyone who doesn't know about nicotine addiction by the time they go to secondary school is a lost cause. They don't want to know or they persist in the belief that it won't happen to them. It's a shame people who are that stupid cost so much to treat.
What's wrong with drinking alcoholic drinks in front of the kids? So long as you are sensible about it and, again, explain the dangers of overdoing it, they know the basic facts. Again, there's enough publicity everywhere about alcohol abuse.
You can teach people as much as you like but if they refuse to learn what they are being taught (i.e. are bloody-minded) what then? Take the blame? No. Just keep on with the same message. There is no reason why any youngster in this country shouldn't understand the basic risks about addiction.
Beats me how smoking and over-drinking are seen as 'cool'.