The obliques aid in compressing the abdomen and in forward-bending. They are also the hard workers that help us in side-bending and twisting our torso.
The big reason to include oblique work in your workouts is to make sure you have tone and good function in any muscle group—you want the full benefits that muscle group has to offer.
In this case, it's the side bending and twisting ability along with abdominal compression and forward bending. Many of us want to make extra sure we get our oblique workouts in because toned obliques make for a nice waistline.
Keep in mind that the obliques work in concert with your other abdominal muscles and really all the muscles of your Pilates powerhouse—abs, back, hips, pelvic floor.
It is not recommended to focus just on obliques, but rather obliques in the context of a full-body workout. We want form and function along with a waistline.
Making bending and twisting exercises effective and safe to get that oblique workout. One example is the Pilates Mermaid Side Stretch Exercise below.