Why I wash fabrics before cutting them.
Actually, now I "marinate" them in hot water, and then wash them in warm and dry on Permanent Press setting.
1) Some fabrics shrink. Some more than others. Sometimes - if the shrinkage is severe - it can even pull out of a seam. I prefer a flat look to the puckered look. And even if I did want a puckered look, I would go for a batting that shrinks and get more or less even puckers.
2) Some fabrics will bleed. (I soak like colors together - so in case something does run, it won't be a disaster.) I'd rather know sooner than later.
I also hope that the recipient will care for the quilt, but I doubt that many of them would know to use a dye catcher or something similar.
Babies are leaky. Sometimes one doesn't catch the leak until it's been there for a while. Sometimes color will be okay/stay put it it just goes for a quick dip, but not for a soak.
(I know this because I had let some fabrics set while waiting their turn to go in the dryer)
3) I like to know what the true nature of the fabric is. Is it limp? (I think using starch/sizing to make it more hefty than it is, is cheating) Using it to make it easier to handle is something else. Are the grain lines perpendicular to each other? Is it permanently off-grain?
4) Some fabrics smell weird when they come from the store.
5) I want to know how badly it wrinkles when it is dried. Some fabrics can be "hand-pressed" - and folded and put away. Some come out of the dryer so rumpled, they look like they were permanently scrunched - and they don't press well.
I do try to handle the fabrics gently - which is why I go for a soak in hot water first - and dry for as short a time as possible. With only a few things in the dryer at a time.