Re. the cannabis v. tobacco debate - the perspective of society is less to do with the parallel harms, and more to do with the cultural status.
Tobacco, like alcohol, is an inbuilt aspect of our culture, and therefore difficult to demonise because it is so widespread.
Cannabis is a relatively recent phenomenon, and is rooted fairly and squarely in its negative 'feckless youth' position in the view of society as a whole.
Cannabis is something engaged in by dubious young people who wear their hair at a challenging length and would rob their grannies to get the money for their soon-come heroin addiction - tobacco is something your granddad used to puff on with his pint, lovely old guy, salt of the earth.
The use of tobacco will continue to fall because it is increasingly culturally unacceptable, and that above all will stop its use - although any measure that hastens that demise has to be welcomed.