You might be over-reaching with your last paragraph. There are plenty of people who drink alcohol around other alcohol-users and the social dynamic limits how

You might be over-reaching with your last paragraph. There are plenty of people who drink alcohol around other alcohol-users and the social dynamic limits how much they drink (don't want to appear foolish or out of control around friends or coworkers, match number of drinks to the people they're with, etc). There are also plenty of examples of people using "party drugs" on weekends socially and that those same friends are the first ones to voice concern if a person in the group starts using the drugs more often or in excess. In many cases, it's when people switch from using drugs with friends to using them alone that is the turning point to addiction and problematic usage.