When teens use tobacco, they often do not think about where their choices in the present will lead them in the future. As tobacco is extremely addictive, their developing brains will become hopelessly addicted and they will start off on a road to destruction faster than they ever expected, just from tobacoo use.
Time and again tobacco products have been proven to be unhealthy products. Minors should not be allowed to use these products because they are detrimental to ones health. As an adult, it seems plausible to make your own decision about products that may harm you, but as a child you are not self aware enough to make that decision, yet.