I assume no one prefers middle seat, therefore people should prefer either aisle seat or window seat on airplane. My personal preference is aisle seat. I have two major reasons to chose aisle seat.
1 - I would like to get off from the plane as soon as possible.
2 - I do not want to bother the passenger sitting next to me when I want to go to the lavatory.
In general, Japanese prefer more aisle seats than window seats. Then, on the other hand foreigner,especially European prefer window seats. You probably should check next time when you are on board.
In fact Japanese seem to go to lavatory more often than European do. I have seen many European sitting on window seat for a long haul flight but not going to the lavatory at all! These passengers are usually sleeping on board.