silly layout/cutting question

Okay--so I'm sewing the Ice Cream Dress for the first time and I'm wondering....is there some reason why none of the pattern pieces are set up to cut out on a fold? I'm a beginning sewist, so I'm not familiar with all justifications for pattern layout. I was just thinking that it would make layout and cutting easier, and allow me to be more economical with the fabric. And I notice that most of the other Oliver + S patterns make use of a fold in layout and cutting. And now I'm just curious....how/why is this pattern different?