Because the Bible teaches us to be moral. In fact, throughout history moral values have been the basis of our education. First parents, then school, and finally universities were teaching us to be kind, honest, sincere, warmhearted, etc. Religion used to be one of the most powerful tools to instill moral values into people. Religion has been losing its influence in many countries around the world. Nowadays it is still important to many, but only for a section of many societies.