Why do you think there are substance abusers that eventually lead to addiction? I think the most common reason would be a family issues and problems. Family should be the first and the strongest support each of use shall receive. But if you are face with family problems, there occurs a strong tendency for us to feel shattered and so we resort to some for of escape. Easiest and the most immediate are drugs and alcohol. This is why addiction often happens during teenage, the age we are most vulnerable.