It's called denial. To a "normal" person their behavior seems crazy. To them it seems normal and not drinking in excess. Often times, the person with the problem is the last to find out they have a problem as the family and friends knew long ago. Denial is very powerful and is not limited to people who suffer from addiction.

And don't worry about you not "buying" it. The FAA, Airlines and modern medicine already "bought" it and have been/are helping people. It is on the list of diseases/disorders that can be treated and given a special issuance medical.

Chances are if you fly for an airline, you have already flown with them and probably had no idea that they ever even had an addiction problem, which means the program is working.

Here's a fun little fact. About 12% of Americans suffer from alcoholism. That's about 2.8 million people. I know you will be understanding if/when you encounter an alcoholic friend or family member...
Alcoholism - Wikipedia, the free encyclopedia


Behavior Patterns of Denial
Family, friends and employers notice changes in the behavior of an alcoholic or addict long before the person with the disease does. This is the first indicator that someone is in denial about their disease. Tragically, as it progresses, the individual barely notices the changes and deterioration because they happen gradually, day after day and seem normal to the sufferer.

Typical behaviors include, but are not limited to: being late to work, inability to hold a job, getting arrested, ending relationships when people criticize their drinking or using, spending rent money on drugs or alcohol, not keeping commitments, driving under the influence, poor personal hygiene, frequenting dangerous neighborhoods, and living on the street.

Again, the alcoholic or addict does not notice or pretends not to notice that these behaviors are related to their substance abuse, when clearly they are.

Denial: Why Alcoholics and Drug Addicts Think it is OK to Drink and Use Drugs | Recovery First