Im sure its already pretty obvious if their kids are locked up at home when theyre smoking thats pretty serious second hand smoke. Or maybe the parents will smoke in a certain room where the kids dont go. Both my parents smoked when I was young and I will never smoke (cigarettes, or become addicted to anything like that). I cant say if it effected me or not, but as far as I can tell it hasnt.
Its kind of like telling them how to raise their kids. But what makes that any different than having a dirty house thats not sanitary for your kids, or feeding them crap food. The government, OR the people (sort of the same thing in this situation) cant really do anything about it.
"The people" can only take action through the government. No one is going to listen to what you have to say, if they are set in their ways, unless its a law, and even then they still might not.
The government decides because the people decide.