Straight of grain is very important for clothing because it affects how the garment drapes on the body. It's not as important for quilting, especially for someone like me who does not prewash fabric (or for someone who prewashes and then starches to restore body and stability to the fabric).
I do not care if my cuts are slightly off-grain; it doesn't make any difference to my piecing. The cut is not enough off-grain to become stretchy the way a completely bias cut would be.
Many directional prints are not printed exactly on the straight-grain, or the straight-grain is distorted at the factory when the fabric is wound onto the bolts. When directionality is involved, it can be more important to cut on the straight line of the print (for example, stripes) than to cut exactly on-grain.
Another reason why straight-grain is more important in garment making than in quilting is the size of the pieces. Garment sewing is typically done by sewing large pieces of fabric together. If the grain of one large piece does not match another large piece, the long seam is going to reflect that when the pieces are draped on a body. Quilting is typically done by sewing smaller pieces of fabric together. Even if all of the small pieces are a little off-grain, these pieces are going to offset each other. If the quilt requires such precise piecing that every thread needs to be on-grain, it is better to do paper piecing (where the grain also doesn't matter).
The only instance I can think of where I might want to pay a lot of attention to straight-of-grain might be on a whole-cloth quilt.
Last edited by Prism99; 01-29-2014 at 02:34 PM.