Muslin has to be preshrunk if used with other cottons or you have puckered patches when the quilt is washed and dried. Some feel you get what you pay for so they use only cottons from other sources and avoid the cheapest cloth for quilting, which is muslin. It does not have the sheen or fine thread count other cottons and calicoes have but it is economical to use. A purist would not use muslin and would not use it along with more expensive cloth.
Carol J.