I have sympathy with some people who get shafted by this (families with young children, elderly relatives etc) but I can never quite understand the amount of wailing that goes about this when you’re on the plane. Sure, all things being equal I’d probably rather travel next to the person/people I’m with, but I’m not gonna cry about the fact I have to spend an hour and a half to Marseilles or whatever on my own. Just listen to some tunes, read the paper, have a nap, whatever. Baffles me how often you see a family with adult children kicking off about it.
Tbh, I often secretly quite welcome not being sat with the person I’m travelling with, especially if it’s on the return journey when I’m fed up of them.