Drug runners can't create demand by sheer force of will.
They don't have to. Heroin use has been increasing all over the country - sadly. Kids get hooked on Oxycontin or some other medicine cabinet drug and find they can't afford it on the black market so they find they can get a dose of heroin for $5 instead of the $20-$50 for Oxy. Next thing you know they're hooked.