Because drugs are illegal, they are lumped to together, one guy who sells one might/probably sell the other. This is also why people call weed a "gateway" drug, because the dealer might have some MDMA or coke on them as well.
If we just made all drugs illegal, I think we would eliminate this "gateway" effect.
The can see evidence of this grouping effect in the mafia. They sell untaxed cigarettes, stolen goods, drugs, etc. What is the commonality between all of these things? The fact they are illegal of course!
Did you mean to write the opposite of this?
https://www.samhsa.gov/data/sites/default/files/NSDUH-DetTab...
This is still the USA. Healthcare is attached to employment. I think it safe to say that those without jobs aren't visiting the doctor, getting prescriptions, at the same rate as those with employer-provided care.