Well, the curves in this fence are symbolic as to the proper cervical, thoracic and lumbar curves, that your spine column needs to be stronger, stable, and flexible. Why you may think that if your spine was straight, it would be stronger that is not necessarily the case. A straight spine will weaken the overall biomechanics of the spinal region, causing injury, tension reduced range of motion and of course pain. 

So let's go over the curves of your spine. The neck or cervical lordotic curve should be a natural C curve. When you have this proper curve, it places your head directly on top of your shoulders, allowing your body to be in a better alignment and not stress causing undue stress on your neck, pain and headaches. The thoracic or middle back curve is a kyphotic curve or reverse C curve, When is curve is not present you were may have middle back pain, spasms, sometimes shortness of breath and undo tension between your shoulder blades. The last of the spinal curves is the lumbar or lower back lordotic curvature. This should also be a natural C curve, which gives the lower back and CORE stability and flexibility. When you have a flat lumbar curve, many times, you'll have back pain, sciatica and difficulty moving, sitting, bending, twisting, lifting objects and even problems getting dressed in the morning. 

Having all of the proper cervical, thoracic and lumbar curves, gives your spine true stability, flexibility and strength. Your spine is 10 times stronger with these curves than without them. Just a note to say that a scoliotic curve are quite different as they will weaken, cause deformity and dysfunction in your spine. Going back to the original fence picture of the waviness of the brick walls. You may think that a straight fence would be stronger which it's not the case. This design uses fewer bricks than a straight wall and is not easily toppled, because the straightness creates weakness. The wavy brick wall stands with added stability due to the arch support system provided by its shape this old crinkle wall. The old English version of the zigzag which is why impressive in the design instability which many of the walls still stand today. So there you have it, this is why you need to continue work on maintaining and getting back your spinal curve because without him, your spine will be weak, unstable and may "topple" causing you pain, stiffness and reduce function in your activities of daily living. Thanks for reading, Dr. Joe.