Clarifying: Nicotine harms everyone. Net harm to a schizophrenic may be negative, but they are still harmed.

"Self-medication hypotheses" exist for many abused substances. Rather than accusing the addicted of poor education, self control, or intelligence it argues (with mounting evidence) that there is a structural or genetic issue that contributes for some addictions.

Ideally we would figure out the mechanism of action and design something with less negative life altering side-effects.

There's always an opportunity to examine freedom of choice/free will for the more philosophic among us :)