The most disappointing thing I ever heard my father say was "I don't apologize to anybody." My mouth dropped open and instantly I felt so much less of him. I felt awful for what my mother had to endure in her marriage, if that was his belief. I think back on it and some of the hurtful things he said about my appearance and you know what, he never did apologize. I just never thought about it until he said he just won't apologize. He has no idea how that has affected me and if he did, well no apology from him, I guess.
I have no thoughts to why a person is like this. It's a great question to ponder though.