Drugs & Money.
Regardless of the vice or the individual one can assess the potential benefit detriment balance according to a hierarchy of needs and prioritization.
As soon as the balance tips towards the detriment to health or personal relationships any individual has to weigh up the perceived benefits of any given behavior.
But how can they if they are stoned?
How clearly are they thinking?
If they prioritize the drug where is the normal yard- stick?
Money is always a harsh objective measurement for defining the scale, as realistically leisure based recreational habits like drinking, smoking is rarely fiscally rewarding.