Why Do people smoke and drink at parties ?

I believe people use substances that alter their mind states at recreational events in order to have an excuse for actions that may be perceived as more immoral while sober. Don't get me wrong, wine and soft drugs like weed are quite pleasurable in moderation, but hard liquor often tastes quite bad and is drunk with the intent of getting ****** up. Do people bear the burden of hangovers just so they can experience the half minded behaviors of the night before?