Obviously, a habit that has a 1 in 2 chance of ending in a horrible and needlessly early death is a poor choice for anyone.
But, I really, really don't get it with models. Smoking makes you look bad. It promotes fat storage on the abdomen, causes mouth wrinkles, wrecks your skin, stains your teeth and hands, drastically reduces your capacity for physical exercise... maybe they think their careers will be over before they lose their looks to smoking.
@Honeybunches, if a model smokes, and I smoke, does that make me look like a model? No. Indeed, plenty of fat ugly people smoke too.
If you're interested in reducing/suppressing your appetite, you could try gum, caffeine, eating more protein, healthy fats and fibre, drinking more water, eating less but more frequently, cutting out refined carbs, reducing salt and sleeping more.
Or you could eat according to your hunger and do more excercise.
Don't start smoking! Good luck.