Lower back pain has many causes, ranging from poor body mechanics when moving heavy objects to trauma (injury or illness) to a body being out of shape and not able to bear the weight that the back takes on.
Because the Western world has changed from an active lifestyle to a more sedentary one, when people do get active, they often injure their backs. Another important issue is job safety. Many jobs require moving in awkward motions or at awkward angles, even if there is no lifting. These can also cause lower back pain.