Another reason for setting seams --- try this test: sew two 3" seam sections. Press one to "set the seam," but not the other. Now "unstitch" both sections. Notice how tight the "set" seam is. Also notice how the thread has been pressed into the fabric. I sew with 50/2 (usually Masterpiece) thread and I set my seams. This way I don't have to rely on my interpretation of what a "scant quarter" seam is.