If I do heroin once and stop for whatever reason (because I didn't like it, because I was afraid of the addictive potential), why would I keep injecting myself

If I do heroin once and stop for whatever reason (because I didn't like it, because I was afraid of the addictive potential), why would I keep injecting myself over and over until the "chemicals did their job"? You're making a big assumption that people would keep going back to it instead of stay the hell away like you and I both do today (presumably). It's illegal but not hard to acquire. For the record I've been prescribed opioid derived drugs and did not get hooked. Why? Because I know how addictive it can be, so I popped some to see what it was like and trashed it. This world where everyone uses opioids pervasively won't happen because people would know or soon figure out how pointless and devastating it is. It's like asking why we don't have cultural customs where everyone murders a new family member each monday. Any culture dumb enough to try no longer exists. In reality there is perhaps a good historical example of mass opium addiction you could tie your narrative to though: https://en.wikipedia.org/wiki/History_of_opium_in_China https://en.wikipedia.org/wiki/History_of_opium_in_China