We've always rode that way,ever since high school, didn't know there's any other way.
When your riding in pack,and you come to a turn,the inside guy goes first the outside guy drops in behind.then back to side by side on the straight.
Unless it's a long sweeping turn,then everyone stays together.
Usually the women passengers will take pictures,and hand stuff back and forth.it makes for a great ride.
Unless you don't know the people and how they ride,then they go to the back of the pack.
Some guys like the right side,I personally like the left side.
But I'll take either.