Have you ever seen an old quilt have had places where the batting has bunch up?? That is what happens when back in the 30s, there wasn't any scrim in the batting. Scrim is like a stabilizer as ckcowl stated. If you do limited quilting or tying a quilt, the batting will not ball up into corners when washed. Cheap batting will still do this so beware what you purchase. Hope this helps.