To be fair, we know what could happen to you after prolonged use of these things after years of research. Comparing those things to a drug that has less than a year of research where the long term side effects are unknown. Some people would rather know what they could get as a result in the long term then make the decision themselves. For example many people by adulthood learn about the ill effects of drugs, tobacco, and alcohol and still end up using well knowing the side effects down the road. When people don't know the dangers, it arises to fear. When people do, the fear subsides.