Why are young people more likely to take risks with their health and safety, including use of nicotine and other drugs?

Young people are more likely to take risks with their health because  in my personal opinion, feel like it may make them feel or look more mature, or they want to experience a sense of "yolo".

Explanation:

Being a teen myself, I would be lying if I were to say I do everything simply because I want to please myself or make myself happy. People can do things, drugs or use nicotine, to feel a high. When you do something you feel is not exactly "good", or something you really should not be doing, you feel a superiority. This makes teens feel special, or cool, and that could be a reason why they do it.

Hopefully that might help?