Pharmaceutical opiate abuse during the OxyContin days in the 2000s. People didn't see it as an addiction to a hard drug because they felt it was safe because the pills came from a doctor. When it was peaking in the late 2000s and the pain clinics were still booming with out of state customers who flooded the streets of other states with cheap pharmaceuticals. Because the product was there, many people got exposure to it that normally wouldn't notably those from the suburbs whos extent of drug use was partying with alcohol and marijuana and wouldn't dare do any hard drugs.
Slowly more and more people began experimenting with it and thought "this isn't as bad as everyone told me growing up, this makes me social and I like the way it feels". We all know how addiction takes hold from there. Use escalates in those who can't keep it to just using as a once in a while event and dependence is formed. Many of these new pharmaceutical addicts tell themselves "hey I'm not that bad, I would never do heroin".
Around the late 2000s, those with authority had decided enough was enough with all this perscription drug abuse and began efforts to try and curb the issue, hoping that cutting off the access to the addicts would force them to stop and they would ultimately have to seek treatment. OxyContin was forced to change their formula to a pill that was less abusable, pain clinics in Florida began to get shut down, stop accepting out of state patients and in general become much more regulated forcing them to no longer be so liberal with giving the medications that ultimately ended up on streets all over the country.
Due to all of this regulation, pills on the street became more expensive as time went on as the suppliers were no longer able to get the amount of pills they needed. Not only were the pills more expensive, people's suppliers who used to have them all the time now had to deal with droughts and shortages. This was what the authorities wanted and would hope would lead to people getting treatment, but anyone who knew anything about addiction knew what was going to happen.
People who strictly used pills began to not be able to get them often and when they could, they were more expensive then their habit could allow. This is when heroin comes into the picture. Those who said they would never touch the drug were given a choice to be sick, get treatment or buy the drug with so much stigma behind it. Eventually many of the pill addicts try it and say "hey its not that different, its much cheaper and I don't have to worry about my dealers not having this" and thus they switch to heroin and don't look back
As more and more pill addicts become heroin users, the negative stigma that those who once refused to try heroin had ends up getting dropped when they see how much cheaper (at first) and available the drug is and over the course of a few years, heroin use greatly rises and the media begins to inform the public and you ultimately have what we are seeing today which is labeled as an epidemic.
Probably nothing that hasn't been said already, but stems got me in that typing mood.