Originally Posted by
DenverBrian
Because the seat manufacturers can make 10,000 sets of 3-abreast seats instead of 3,300 sets of 2-abreast, 3,300 sets of 3-abreast, and 3,300 sets of 4-abreast.
The different types of 3-abreast seats are not interchangeable.
Left aisle, right aisle and center section seats are different part numbers and cannot be swapped. So there really isn't a significant economy of scale due to that.