Why Can't People of Religion Ever Just Admit That They Might Be Wrong?

I've had a lot of debates online with religious people, mostly Christians. Sometimes these debates are interesting, sometimes they are enlightening, more often though they are simply arguments intended to prove one is right rather than trying to learn the other person's opinion or to understand their point of view. One thing that I find really negative and annoying though is what seems to me to be a complete inability for Christian believers to ever accept that they might be wrong. Why is that?

Countless times I've commented on a blog post, engaged in conversation on a youtube video, et cetera and become involved in lengthy conversations about religion and atheism. I try to only engage in these conversations when they are respectful, I have no need for hateful, ignorant conversations. Some of these conversations have been truly enjoyable and enlightening. There is one acquaintance I have with whom I often converse online and I very much appreciate his perspective and his deep desire to make the world a better place. But, I find that almost without exception, someone who has a religious belief is unable, at the conclusion of a discussion, to ever accept that you've constructed a rational, logical argument that comes to a conclusion that cannot be denied. The conversation always ends with something along the lines of: "Well, I guess we'll have to agree to disagree." Why is this?

My opinion on why this happens is because of the foundation of the belief system that the religious have. Their beliefs are not formed following rational logical thought about the nature of the world. Rather, their primary belief is based on revelation and faith. For example, a Christian is, by the very definition of what it means to be a Christian, unable to ever accept that Jesus did not exist. Therefore, they may enter into an argument about the possibility of the existence of Jesus, but their end point will always be that he existed. Even if you present a rational, logical, and evidence-based case for how unlikely it is that Jesus ever existed (just as an example), the conversation will have to end with the Christian saying that they will have to disagree with you, even if they have no ability to respond to your points. It's either that, or they have to admit that you have made your case and decide not to be a Christian anymore. That's usually not an option in one conversation.

The topics that I encounter this phenomenon more often are those relating to science and evolution. No matter how much evidence you present to a creationist, they will always simply end the conversation with: "Well, we'll have to just agree to disagree" because they are fundamentally unable to change their point of view, even if they've been shown the error of their belief. This is fundamentally opposed to the process of discussion used in science. At a scientific meeting, no scientist will ever simply state that he/she has to disagree with someone after they've been shown conclusively to be wrong. They accept their error and move on, humbly.

To me, this is another example of Christians putting the cart before the horse, of drawing your conclusion before you look for evidence, and of the immense arrogance of their position that there are certain pillars of their belief system that they will never give up no matter how wrong they are shown to be.