Because they are alcoholics and drink whenever they can.
There is nothing to do in an airport or an airplane. It’s like solitary confinement. All you can do is eat, drink, maybe buy a shitty book from the local duty free shop, and wait out your sentence.
A terribly uncomfortable experience.
I get this, but I've also met some interesting people and sometimes found myself deep in honest conversation for hours at a time. I'm saying this as someone who is usually reserved to the point of being anti-social.