Well, the thing is that for a great many of us, ‘sorry', actually, IS the hardest word. For example, some people cannot admit their mistakes because pride and stubbornness take priority over relationships. They perfectly understand what consequences their stubbornness can lead to, even so, they cannot do anything to change themselves. There are also those who don't want the other person to feel that he or she has any power over them by giving him or her the choice to accept or reject the apology, especially when their wrongdoing is not that serious.