China has always been densely populated, often even overpopulated. Why did the Chinese not populate the neighboring, sparsely populated lands as the Russians, Spaniards, and British did later?
The lands adjacent to China require a different farming culture: either the cultivation of wheat with rain irrigation (in Manchuria), or tropical vegetable growing (in Indochina). The indigenous Chinese – rice growers and millet sowers – did not want to master the barbaric way of life.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.