Also because our ancestors pieced by hand and it did make the seam stronger because there was less stress on the stitiching.
Originally Posted by Scissor Queen
Mostly because we do things the way our ancestors did. They pressed seams all to one side to keep the batting in. Batting wasn't bonded or needle punched, it was just carded cotton laid on the backing. Plus hand sewn seams have little tiny gaps in the stitching if they're pressed open.
Carded cotton is sort of combed between two wide flat brush type things. They pull all the cotton fibers in one direction.