I think a lot of it is based on how little of time most people knew existed in a tangible way. Until the last few centuries you were born into a world where most technologies you use had already been around so long they just might as well have existed forever. And the stories of how any talked about technologies were generally myth, folklore, or completely false. The idea the earth was around for billions of years wasn't really a thing for most cultures. Maybe you believed it was around forever, or that a mythological creation even happened in the 'more recent' past and the earth popped up like it was. The idea their was a beginning a long time ago, but it only started out with the most basic shit (ionized hydrogen mostly) and everything after that is because of an ever increasing entropy gradient is just not an idea that seems to pop into our heads.