We always want to strive for beautiful looking sketches but we must remember when we need a FLAT and when we need an ILLUSTRATION.  A flat is a FLAT for a reason.  Illustrations can be over-stylized, more artistic and is mostly for the purposes of presentation and mood as opposed to something you can use in a Techpack. When a garment is on a figure in a pose it may be hard to see all the details of the  garment.  Your pattern maker, factory and also buyer needs to see the garment exactly for what it is and an illustration can sometimes skew this.  Yes we can have different drawing styles to our flats but we need to make sure that everyone in the industry can “read” your sketch.
Below is an illustration done in Adobe Illustrator.  You can see how this may be hard to see the details like stitching, hardware etc.