In spite of being the most complex culture in world China did not expand outward because?

This statement is not entirely accurate. While Chinese civilization is indeed one of the oldest and most complex cultures in the world, China has historically expanded its territory through various means throughout history.

While China did not engage in large-scale territorial expansion in the same manner as European powers during the Age of Exploration, it did expand its control over neighboring territories through military campaigns and diplomatic negotiations.

However, it's important to note that China's expansion was often driven by specific geopolitical and economic interests rather than a desire for territorial conquest for its own sake.