lots of people don't prewash for lots of reasons. you have to do something to the ends so they don't turn into a thready mess.
you have to separate colors to avoid bleeding or use a color catcher or synthropol. and then you have to fold and press.
sad to say, there are no shortcuts that i ever found to work.
others prewash because because fabrics are not woven to the same thread count and will shrink unevenly. if the colors are going to bleed let them bleed now. if the fabric is going to end up limp as a rag let it happen now. if the fabric has been exposed to harmful chemicals (they are) not everyone wants them in the sewing room. fabric is manufactured in 3rd world countries and brought here. what else came along for the ride?
also, i recently was given fabric that i thought wasn't good enough to use, but after prewashing, it shrunk in and got tighter. so, fabric that i would not have used before, i was happy to use after washing. score one for me.
i'm a firm believer in prewashing. i want to know how much fabric i really have after shrinkage and warping, even if it means more work for me now. as for the 'wrinkly look', batting shrinks enough to get that look anyway.