Why are technical flats the go-to format to communicate designs in fashion? They communicate so many aspects of the product throughout the development process.
To designers, they communicate the proportions, design details, and overall silhouette of the design.
To a patternmaker, they communicate what finishes you want and where each section of the garment (sleeves, front, back, etc.) come together.
To a tech designer and to your factory they communicate (when combined with technical callouts) what types of seams and stitching you want on the garment.
To sales, they clearly and quickly communicate the products for sale on a line sheet.
Because flat sketches are all about communicating the details of a design in black and white (literally), it is important that your flat sketches are accurate down to the smallest bartack and button.