Slimmingmom, for me the "bigger picture" is freedom. Freedom is the most precious thing we Americans have. Just look how scarce it is in other countries. Absolutely frightening.
If a child is living in an abusive home, state law allows the child to be removed from the home and even allows the parent to lose his/her parental rights. But it makes no sense for the government to micro-manage parenting. If you're unlucky enough to be born to parents who put their desires before your needs, the government can't really change that unless the behavior rises to the level of abuse necessary for child services to take action.
Guaranteed a parent who smokes in a car with little kids is doing a lot more stuff inside the privacy of his/her home that we all would find abhorrent. But, like Beavs says so well, where do you draw the line? To me, that's the big picture.