I DO NOT LIKE the puckery look at all. I even prewash my cotton or cotton/poly batting to avoid that. I like my quilts to look as much like they did when first made as possible after washing.

I always prewash my fabrics, due to allergies and asthma
I don't want my carefully pieced blocks to shrink weirdly.
All the chemicals that are used to process the finished fabrics can't be good for us to be breathing.

And that's fine. Many people like puckers, many don't, and some of us (me for one) don't care that much, or make the decision on a quilt-by-quilt basis.

That's why I prewash also. So if you don't and one piece shrinks 3" and one piece doesn't - what a sad looking quilt! I know the ironing is a real pain, so is sandwiching it all together. Unless it's an art quilt that will hang on the wall, I always do wash.

OTOH, I've begun my quilting journey with a couple of kits (because of fear of color selection), and the instructions for those definitely say DO NOT PRE-WASH, as the fabric pieces are cut either specifically to size, or the amounts provided would not be sufficient if they shrank. So, I accept that I will have shrinkage, and fortunately I like that puckery look. However, since the fabrics in the top are not pre-washed, I feel that I shouldn't pre-wash the backing fabrics either. Or the batting. Does that sound right to you experienced quilters?

And fabrics for any of the art quilts that are fused should be prewashed anyway because the fusible will not stick to the fabrics otherwise.

I have never pre washed fabric. My quilts just get puckered after washing once quilt is done. I have never had a problem with it shrinking too much and making it wonky. 99% of the ladies I quilt with don't pre wash.

Somebody told me years ago to cut a tiny triangle off each corner of the fabric to be washed. It really does seem to keep the stringiness problem down. I hate all those twisted, knotty strings.

Yes! Don't prewash any of it.

I always prewash. Even FQ's. And I never wash the completed quilt before gifting it.