Sure it is easy. As we age our tissues sag, think of the bags under your eyes as like a beer belly. Technically the orbital septum gets weak and instead of being like a flat young belly starts to sag, it holds back the fat in the eye socket, the fat follows the weak septum and bags develop. Some things make them worse: thyroid eye disease, use of steroids, obesity, heredity. Time and gravity are not friends to human bodies.