This is a habit. Most people will use this because it is convenient, of course, if you can use it. If you can't, it doesn't mean that your clothes won't look good. In a sense, CAD is just a tool to improve efficiency.

If your design is really good, why care? Finally, it depends on the clothes, not the drawings. Can be hand-painted. The ultimate goal of fashion design is to make clothes look good. It's not how skilled CAD is