The heroin number appears to be lower because it's a more addictive drug than cocaine. Users are less likely to try to quit. What's more important to consider

The heroin number appears to be lower because it's a more addictive drug than cocaine. Users are less likely to try to quit. What's more important to consider is that treatment is not always voluntary. A sentence for a marijuana-related offense frequently requires that the convicted seek treatment and pay for it out-of-pocket. Treatment rates influenced by compulsory attendance cannot be trusted as accurate public health data.