Most people use it because it makes them feel good. Then some have to use it to feel normal. Eventually they find they can't stop without feeling as though they are going to die. About 85-90% of...
Alcohol is useful to cleanse things. Alcohol can kill bacteria. Therefore it is often used in a disinfectant. You can also use special alcoholic sheets that can help clean out a cut.
Most teens use drugs because they are -bored-depressed and see no other way to be happy- this was probably influence by "friends" that were also using-curiousity-peer pressure-mother/father/sibling...