Pilots have problems like anyone else and have to also be protected from themselves.
The Japanese railway requirement of a breath test on signing on would do just that!
A pilot who had been on the binge the night before for whatever reason would call in sick rather than try to get away with it if he had to blow into a machine
It would save his job from a stupid decision mistake as well as maybe a plane load of passengers so win win all around and the cost a 30 second blow
Pace