It's not because they don't dare to but because of the respect rooted deep in their heart. The respect they hold for the Grand Moon Chalcedony Empire that once ruled the entire Awakened continent. The seven kingdoms came into being after the Grand Moon Chalcedony Empire vanished from the face of the world. According to history, the Ancestor of the seven kingdoms used to be citizens of the Grand Moon Chalcedony Empire. That's why they respect the Empire. It's their roots.
The seven kingdoms had a silent agreement. Only after a kingdom manages to unite the entire continent under its rules will it be worthy to be named an empire. Each kingdom wishes to become the next empire of the awakened continent; However, not even a single emperor was capable enough of achieving such a task.
