I prewash every piece of fabric I buy. Even jelly rolls. I just washed 3 sets of jellyrolls tonight. I swished them around in the sink with warm soapy water, ran them under running water to rinse, squeezed them out, and put them in the dryer. They came out wrinkled, but intact. Just have to iron and starch them.
But that's just my preference.
However, I sewed clothing for many many years, and ALWAYS prewashed garment fabric.