More and more I wash fabrics prior to cutting out a garment. Actually, I frequently wash them before adding them to my stash. As clothing has become more relaxed and less "buttoned up" fabric that doesn't look brand new is more stylish and comfortable.
Here is a photo of some linen yardage.The piece on the left is unwashed and the piece on the right has been washed. The picture may not show the contrast very well, but I much prefer the look and feel of the fabric on the right.
If after the first round the fabric still hasn't softened to my liking I will repeat the process.
I have washed all types of fabrics including silk and wool. A hard finished wool that looks like it needs to be made into a very tailored garment can soften and get a little "fuzzy" making it suitable for a more relaxed styled garment.
It is no surprise that this process will frequently shorten the yardage, sometimes significantly, but the surprises that emerge from the dryer are often very exciting!