It seems like you're questioning why some atheists do not believe in a creator despite the lack of a comprehensive explanation for the origins of the world through evolution and the Big Bang. It's important to note that atheism, in its broadest definition, is simply the lack of belief in gods or deities. Atheists may have different reasons for their disbelief, and it's not necessarily related to the scientific explanations for the origin of the universe.
Regarding your analogy with a passing car, it's worth noting that the existence of a car does not automatically imply a supernatural or divine creator. We have a clear understanding of how cars are manufactured and how they come into existence. However, the origins of the universe are a complex and ongoing area of scientific inquiry.
When it comes to the origins of the universe, both the Big Bang theory and the theory of evolution are scientific models that attempt to explain natural processes. They are based on empirical evidence, observations, and rigorous scientific investigation. These theories provide explanations for how the universe and life developed and changed over time, but they do not address the question of ultimate origins or the presence or absence of a creator.
Many atheists who accept these scientific explanations may do so because they find the evidence compelling and the explanations consistent with observed phenomena. They may see no need for a supernatural explanation when naturalistic explanations can account for the phenomena we observe in the universe.
It's important to remember that atheism is not a monolithic belief system, and different atheists may have different perspectives and reasons for their disbelief. Some may base their atheism on scientific understandings, while others may have philosophical or personal reasons. It is always best to engage in open and respectful dialogue to understand individual perspectives rather than making assumptions about a diverse group of people.