This has almost never happened to me when flying maybe 20 flights with Southwest together with someone, but it has happened with traditional airlines like Ameri

This has almost never happened to me when flying maybe 20 flights with Southwest together with someone, but it has happened with traditional airlines like American or Delta when they have full flights. With SW if you buy the tickets together, and check in first possible moment (24h before), you get assigned the same boarding position, usually a early B number. Then you board together and likely half of the plane is likely still empty when you board. People also sometimes say they are reserving the seat for someone. Have never bought priority boarding.