Have you ever tried to perfectly fit a sleeve into a sleeve cap? Or a Peter Pan collar onto a neckline? Or just to measure around a curved opening on a garment to figure out how much binding to cut? I've tried various methods - trial and error (ick!!), using a piece of yarn and then measuring and flexible rulers - but none has been accurate enough for my satisfaction.
Enter Adobe Illustrator. When designing sewing patterns, you can easily measure curved paths to make sure your pieces will fit together precisely without printing and cutting (and printing and cutting and printing and cutting, repeat, repeat).