Well I think the first issue you may have is that you seem to think that their beliefs are held due to some ulterior motive of not wanting to be held accountable. That’s simply not true. For most of them, despite you disagreeing with them, their beliefs are sincere.
As you said, the word of Christ either sparks them as righteous and true or it doesn’t. For them, it simply doesn’t.
But people do have ulterior motives at times to believe something.
Jesus gave the example of building your life on a good foundation. He compared building your life on faith in God as building it on rock, but not doing so was like building it on sand.
Building a house to live in takes a great deal of time and effort and money, as the longer you go the more you have invested in it, and as as result, the more you want to finish it and protect it. And once it is complete, there is precious little as important to you materially. It then behooves you to try and protect that house of faith or atheism at all costs, the more you have invested in it. I think those of faith who glibly give up their faith don't have a lot invested in it. They probably thought they were Christians because their parents were, but there is nothing in their lives that are dedicated to living a Christian life. In fact, they probably have never even read the Bible. So giving up that "belief" is not that difficult for them. However, if your entire life is dedicated towards the gospel as you make all your friends in that arena and maybe even your livelihood, the more you are invested to protect it, etc.
Likewise, when people build their "house" on atheism, especially if they make a living off it in some way, they become more and more invested in it to protect that investment. Take Richard Dawkins, for example, he has dedicated about half his life to making fun of Christians, writing books on end about how wrong it all is. To then come to the conclusion that he is wrong, would mean taking a hit in his pocket book, as well as his pride. It therefore becomes less likely.
In addition, the Bible says to teach a child the way he should go and they will not depart from it. This means beginning to make sense of the world as a child which means creating a belief system in order to make sense of the world. Belief systems are really the only way we can make sense of the world, since we can prove precious little outside of a math class. The more you include God into the woven fabric of our belief system, the more important he is to maintain that in order to make sense of the world. The opposite is true for those not of faith. But if you mature to adulthood and are compelled to give up your former belief system, it is a traumatic thing because you have lost your ability to make sense of the world and must start over. You loss is great, but your gain is far greater if you choose wisely in the correct belief system. It simply takes courage is all, something many do not have.
What I find miraculous are people who give up that mansion built on a faulty foundation, such as Paul in the Bible. He made his living as a Jew persecuting Christians. He had a lot invested in his way of life. Yet he later gave it all up after he converted to becoming a Christian as he spent him time running from authorities to proclaim the same message he once tormented and murdered people for giving, as he too gave up his life for the sake of the gospel.
