The guy who made the drugs is guilty. The guy who sold the drugs to kids is guilty. But parents who failed to warn kids about drugs and to oversee them properly are also guilty...
Now if we're in a discussion around the cartels, plenty of people do bring up (and there's also those that get annoyed by it) that the drug users are actually the ones funding the cartels via their drug use.
Along these lines, I think another fun comparison might be opioid use and Purdue.
eg: I grew up in a very nasty place. My neighborhood had a few pregnant 13 year old girls and a lot of drunks and smokers, including kids in their early teens. My parents kept me away from it all, while also both having full-time jobs. They put a lot of work into filtering whom I could be friends with and where I was allowed to be. THAT is the job of a parent.
Maybe you don't do this. Certainly I don't. But when looking around, its much less rosy and... lets say in blue collar families its too common to drug kids with screens so parents have off time. Heck, some are even proud how modern parents they are. Any good advice is successfully ignored, and ideas of passing some proper time with kids instead are skillfully avoided. People got lazy and generally expect miracles from life without putting in any miracle-worth efforts.
Companies just maximize their profits till laws allows them (and then some more), and expecting nice moral behavior by default is dangerously naive and never true.
But sure, "Parents often give too little fucks for long term welfare of their children", that's definitely it. Parents just hate their kids! What a useful perspective you've brought to the discussion.