People don’t change. People may grow, and entertain different aspects of existence, but base nature of a human’s experience is unchangeable.
This is an uncomfortable prospect for the human mind – we want reasons, we want rationality, we want logical development. We want things to make sense in order to better understand, but things just are.
So we like our characters to learn a lesson, we like to see them have character development where they go through a character arc. Why? Because we desperately want it for ourselves. We want to have it for ourselves so we force our stories to follow the myth.
Me? I don’t want it in my characters, it makes me curse because it’s so transparently false to me. I suppose this is why I love Brian Kinney from the US QAF, why I love Spike from Buffy, why I love Greg House from House. They don’t change (Spike always conforms to the wills of his love, etc.) They may act differently from time to time, but they don’t develop just as we don’t develop. We don’t change.
Writers who understand this aspect of reality and can still make intriguing characters in the modern expectations of a character’s role have my admiration and respect.