Most flights are available at high frequencies (on the order of days, weeks) compared to concerts (once a year or so). You also don't care as much about sitting together on a plane.

You care just as much on a plane. Sitting beside wife/friend => stranger

I disagree, if you can't get seats with your friends in a concert, you might just not go because the social aspect is part of the experience, but if you can't get neighboring seats on a plane, you'd (or at least I would) just tolerate it since you would still get to be together at the main event (the destination).

This position sounds bonkers to me. I don’t care at all about who I sit next to on a plane but like to see concerts with friends.