Because this isn't China - as I already posted:
“Genetic factors account for about half of the likelihood that an individual will develop addiction. Environmental factors interact with the person’s biology and affect the extent to which genetic factors exert their influence. Resiliencies the individual acquires (through parenting or later life experiences) can affect the extent to which genetic predispositions lead to the behavioral and other manifestations of addiction. Culture also plays a role in how addiction becomes actualized in persons with biological vulnerabilities to the development of addiction.” - American Society of Addiction Medicine
Yes, we know it isn't China, but humans are humans no matter where on the globe they exist, and they are susceptible to the same afflictions wherever they reside.
Occidentals are just as susceptible to opium addiction as are Orientals.