Drinks on a plane

Things people do on a flight:

• Knit
• Share upcoming vacation plans with complete strangers 
• Queue for the bathroom 
• Wriggle annoyingly in the seat in front of you
• Drink

The middle-aged mother, accompanied by her husband and bride-to-be daughter, had a vodka cranberry. The angry aging hipster in ochre skinny jeans had a mini-bottle of white wine by Hacienda. The DC wonk behind me having his ear yapped off by a Midwest housewife ordered a red wine (which I assumed was also in a cute little bottle). 

Why is it okay to drink "alone" only when on a flight? I mean I always feel kind of strange being the only one ordering a drink with dinner (though I have done it on several occasions). And drinking alone at home just makes me feel like a total loser (and hasn't always stopped me either).
I state: there is rarely any excuse to drink bad wine, but here go my best guesses at why people feel no shame for being on the bottle while in air. Is it to kill the nervousness of flying (as I suspect the angry hipster suffered from, what with all the twitching and bitching)? Is it to deal with your yippy seatmate, as in the case of the policy wonk? Is it because you rarely have an excuse, and, what the hell, might as well throw one down the hatch? This was my best prediction for the family woman. I am all for a stiff drink to calm the nerves, but I just didn't feel like being off my game when the plane landed. Plus I had to drive. Cheers!