There are many different types of massage, all of them with the goal of promoting healing and full body health.
Proper posture is important because it keeps the bones in the body doing the majority of the work. Vertical stacking, ie, keeping the bones properly aligned on top of each other, transfers the weight of the body directly from one bone down to the next, with minimal impact on the muscles. A goal for life is healthy living. As part of that, people who have healthy, flexible muscles can experience less pain on the day to day. Proper posture keeps the bones doing the heavy lifting, allowing the muscles to relax.
Having a desk job often results in people with rounded forward shoulders. Over time, this can cause tightened pec muscles. This limits the amount the shoulders can go into a proper vertical stacking alignment.
Often coming from having a desk job, or having a sedentary lifestyle, the quads get shortened over time, causing a forward rotated pelvis. this can lead to lower back pain. Releasing the quads, IT band / TFL and iliopsoas muscles can help alleviate lower back pain.