I sell at craft shows. I always prewash any fabric that will be in an item that is for sale. The last thing I need is for a customer to get it home wash it and bleeding ruins that item and potentially the other items in that load of wash. Or one piece of fabric had a rate of shrinkage more than the others that created a distortion of the item. This is particularly true for table runners. If the buyer purchased a flat runner , they want it to stay flat. A dissatisfied customer is bad for business. Repeat customers is the backbone of business.
I do use light starch prior to cutting the get a good crisp final project.