I remember them well. They stopped using them back when knits fabrics came in to popularity. The knits would stretch as they went through the machine , and when the machine made its cut , the measured amount would be short once the knit fabric retracted back , once pulled out from the machine. During this time quilting cottons became a very very small portion of what was sold.
So many quilts made in this era are from double knits, as that was what was popular. Irons almost became obsolete during this era. Poly or poly blends were the perfered fabric , as they required no ironing.