You wouldn't steal a dress.

Fun fact: you can't copyright a dress. You can charge for access to a pattern. Hell, you don't have to make a pattern available. But ultimately if someone can figure out how to copy your design they can. This is part of why fashion changes so quickly. Once you design something it's only a matter of time before someone has copied the pattern and is reproducing it on the cheap. As a fashion designer you have to produce new designs often in order to continue to profit from your designs.