If you are unable to refrain for 2 weeks, then you are not the kind of person who they want to hire, because it means you will also not refrain when you are on duty.
Its a different sort of refrain problem. We expect you'll refrain from activity X when we tell you to for a short reasonable period of time. When X is smoking weed this is seen as a big problem, mostly by weed smokers. When X is applying electrical power to this machine's cabinet someone is working in by hacking around the lockout-tagout locks, this seems a common sense test for a jobsite. We can't test for the latter but we can proactively predict by testing for the former. There are plenty of blue collar jobs where lack of awareness and self control and logical analysis of cause and effect mean someone dies. Weed smoking is a simple test of self awareness and self control and intelligence (WRT understanding the whole problem situation)
