I was lucky. My mother smoked until I was 14, and I was so disgusted by the habit, that I never really had the urge to even try that. I took two puffs on a cigarette in college, and it was enough for my entire life.
Some people can maintain their weight easily, others have a great deal of trouble maintaining and find it almost impossible to lose weight. Frequently, it is not because they are weak or lack willpower, but it is because it IS HARDER FOR THEM.
The same is true with cigarettes. I think those that can easily give them up gave them up long ago. Those that can give them up with moderate difficulty did a little later. Many of those who are still hooked by demon nicotine have a serious addiction.
Remember — putting them down doesn’t help their situation at all. Try compassion and support.