When we are young children, the world is largely incomprehensible and irrelevant to us, as some distant quasar is to us as working adults — at best a curiosity. This changes in our tweens and early teens, when we begin to appreciate that the world does have a certain arcane order to it, that it works in certain ways, or rather that it’s supposed to (recognizing that things work also means recognizing that they break down).
But at that age, much of it is still opaque, which may be why, as a young teen, I was fascinated by books with cutaway art depicting the inner workings of things: weapons or spaceships or castles. I especially loved cutaway hideouts — secret lairs, haunted houses with hidden passages, or even fictional factories like Santa’s workshop. The more complicated and fantastical they were, the better. I even drew my own.
I suspect it is a way for the developing brain to bridge the child’s world, which turns on mystery, with the emerging adult world, where everything turns by cog.