In fact if you read up on the history of the war on drugs, usually it wasn't even motivated by public health. Alcohol was first made illegal largely because of anti-catholic and anti-Irish sentiments (also, interestingly, as part of the women's movement!). Marijuana was made illegal because it was associated with Mexicans. Psychedelics were cracked down on because of the hippies. Crack possession carried harsher penalties than cocaine because it was used by poor black people.