You made it their business when you applied for a medical and asked them to determine whether you meet the standards for said certificate. They don't care about your daily life. They care about whether you meet the medical standards and continue to do so throughout the life of the medical certificate.
You realize that heavy consistent drinking have physiological and psychological results that last long beyond the period of intoxication right?
Hell, so long as it's been 8 hrs since he drank and his BAC is <.04 he's technically legal. If you knew the pilot of the airliner you were about to board spent the last 6 days with a .16 BAC running around their house naked would you get on the plane? Would you want someone like that doing approaches and departures over your house?
.16 BAC is not "normal". Here are some of the common symptoms exhibited at .16 BAC:
Depression, nausea, disorientation, motor impairment, blurred vision, judgment more than "severely" impaired, vomiting (unless tolerant), loss of auditory information processing, slurred speech, increased reaction time, emotional instability, loss of consciousness.
These are just the things the chart lists for the .16 category, they don't even include all the things listed for the lower BAC levels.