Let's look, amorally, at why China has a serious interest in not having child labor.
1. It cheapens their labor, and trades an adult's job for a child. Most of the money for the jobs with potential child labor is coming from out of the country; why not soak them for a few more Yuan per person?
2. It upsets their primary business partners and reinforces the "China regularly violates human rights" stereotype that the West uses as a cudgel.
3. It trades a worker's future gains for much less siginificant short-term gains. China wants more highly-skilled jobs for its young people. It wants more Chinese luxury goods, and wants them sold the world 'round. Every child working in a factor is another child that isn't getting the education to make China a bigger world power and take the reins of a given industry.
All of which is irrelevant to the fact that the best option for many children (again, revealed preference) is to work, and depriving them of that option is likely to lead to a net worse condition.
But to your point, I'm quite certain that "China" would prefer to have an economy sufficiently productive and wealthy that child labor is no longer a choice parents feel they need to make. Banning the effect does not change the cause.
1. It cheapens their labor, and trades an adult's job for a child. Most of the money for the jobs with potential child labor is coming from out of the country; why not soak them for a few more Yuan per person?
2. It upsets their primary business partners and reinforces the "China regularly violates human rights" stereotype that the West uses as a cudgel.
3. It trades a worker's future gains for much less siginificant short-term gains. China wants more highly-skilled jobs for its young people. It wants more Chinese luxury goods, and wants them sold the world 'round. Every child working in a factor is another child that isn't getting the education to make China a bigger world power and take the reins of a given industry.