Double-breasted

I was looking for a brightly-colored rain jacket for a Manolo for the Big Girl reader and noticed that most of the jackets I can find are double-breasted. In my opinion a double-breasted trench looks lovely on Audrey Hepburn, but not so much on a gal blessed with curves. It makes one appear more wide. Why is it that so many plus-size designers don't understand the voluptuous figure.

On a different note, I am lusting after this Gayla Bentley dress and blouse. I love how her Obi Sash gives the silhouette and defined waist.