Why is it so hard for ppl to apologize?

Because apology is a form of self-denial. And to add insult to injury, apologies are usually worthless. "Sorry" or "I apologize" are null words.
I almost never apologize for anything or at least try not to. When I do something, I do it because I think it's right. If it wasn't, is more important to explain how I came to the original conclusion and why it was wrong. Then people - including myself - can learn something from it.
Maybe I had wrong information. Maybe I drew wrong conclusion from them. Saying "sorry" does not mean anything. Saying why has a meaning.