From
kass_rants:
If It Ain't Broke...You see, in the medieval and Renaissance periods, people had to make use of every scrap of fabric. Labour was cheap and fabric was expensive. In the early modern period that followed, wealthy people wore lace collars that would equate in price to an estate in Ireland. So you see where I'm going with this. If you had an expensive piece of brocade, it probably cost more than your house. So when you made something from it, you pieced it and turned it and used every last scrap.
Modern dressmaking techniques waste a lot of fabric. They are engineered for speed of sewing. In the periods we study, speed was not as important and conservation of fabric.