I Don't Understand Some People

I just don't understand, when someone hurts someone else, why they can't just own up to it.  Why can't they say, "I was in the wrong and I'm sorry."  Obviously no one wants to admit being in the wrong, but when you are, be a grown up about it, stop blaming others or finding excuses why they deserve to be treated the way you're treating them, and everyone can  move on.  When I realize I've said or done something that has hurt someone, I feel awful.  I don't try to make that person feel worse by blaming them for my actions.  It's just too bad that some people would rather go on hurting others, instead of admitting they were wrong.