That's nonsense. If you have a private drug habit and don't get caught, that won't come up on a background check. Lots of people consume recreationally without being addicts or messing up the rest of their lives. A conviction (sometimes just an arrest record) that comes up on a background check will automatically put applicants in the reject pile in many jobs. This is such a common problem some US states (eg California) have passed laws to prevent employers demanding this information of applicants.