Flat patterns are the standard in the knitting world and we rarely give the concept any intense consideration. (Many designers of woven fabric use draping techniques instead. To do this you have to work with existing fabric to cut and pin into place).
Stop for a moment and think about this. We take a one dimensional piece of knitted fabric and wrap it around a three dimensional body that is made up of many planes and angles, and then we are surprised that it does not fit well. Add to that the varying individual shape of women's bodies. It’s no wonder that Knitters struggle with fit. Many fitting adjustments are tiny little shaping changes that need to be assessed with a garment on the body to see just how much fabric needs to be added or removed.
If you take pattern drafting classes to develop your own pattern for fitting, the final step is a trial garment. Corrections are made to that garment and then those changes are transferred back to the pattern. The most talented custom clothing creators all do several one on one fitting sessions, before a garment is completed. Couturiers have mannequins created to match the bodies of their clients so that fitting can be customized. Your fit can be continually improved if you begin to keep careful notes about your personal fitting preferences.
But we knitters, we create the fabric at the same time we create the garment and don't always appreciate just how complex what we are doing really is. Maybe we need to appreciate how very special what we are doing really is?