I think the reason for not smoking has to do with hishtadlus. Smoking doesn’t directly cause anyone’s death. It is possible to smoke and live a long life, and it is possible to not smoke and die young. According to Mesilas Yesharim and Chovos Halevavos (and other mussar sefarim), it’s not the hishtadlus that causes things to happen, it’s that we are supposed to have hishtadlus because Hashem said to (and if don’t listen to Hashem and do the proper hishtadlus, we might end up dying), but since we are only doing the hishtadlus because Hashem said to, it only makes sense to do hishtadlus that is according to Hashem’s Will. If we do hishtadlus that is not according to Hashem’s Will, we won’t gain anything from it.
We are not allowed to do hishtadlus that involves doing an aveira. So if the only way for someone to avoid smoking is by not being shomer negiah, it is better for them to smoke, and they gain NOTHING by not being shomer negiah instead of smoking.
Movies is slightly more complicated. While I would say as a general rule that movies are worse, there are many factors to take into account. You can be talking about a boy from a background where movies are normal and smoking is not, and he has a choice between watching a movie that was made for 3 year olds as opposed to becoming addicted to smoking. Or you can be talking about a boy from a background where all movies are considered treif, and the choice is between watching a clearly treif movie or smoking cigarettes temporarily and not enough to get addicted.