Your local craft store can be a great place to buy raw materials such as fabric, buttons, zippers, and more. However, retail stores often phase out products, whether to sell new products instead or because the product itself has been discontinued. If you get your raw materials from a craft store, keep in mind that you may not be able to buy the same materials forever, which could mean you can no longer offer the same products. (Employees at the store, including upper management, usually won't have access to information on whether a product is going to remain in stock for the future, especially at large chains.)
For example, if a fabric goes on clearance and stops being available at your local craft store, and you were relying on a supply of that fabric to continue a product line, you may be out of luck unless you can find a suitable substitute or another source of the same fabric. For this reason, it's often better to get your materials directly from a manufacturer or wholesaler when possible. They'll often cost less, too, but you may need to buy more at once.