Because we regulated it when it got bad. Other countries have had opioid epidemics and they’ve had to intervene. China is a very famous example because the British didn’t like the crackdown as it affected other trade
But how do you explain the fact that, before it got bad, it wasn't /already/ bad. You've gotta have some model for why there was a change if the rate wasn't previously at 100% and the claim is that the number "should be 100% unless it was regulated"
We regulated it as a means to police certain communities.
Hell, Billie holiday suffered from addiction but that bastard Harry Anslinger ordered doctors to not treat her and not provide her with methadone. She died with police stationed at her hospital room door. The FBI also harassed her over songs about lynching.
Nixon is literally on tape saying to go after weed and heroin more harshly as an excuse to arrest more anti-war protesters and civil rights protestors.
I'd argue "cracking down" has done little for controlling drug abuse and has primarily been a method for selective policing. Particularly in the states.