There is little financial gain to be had from raising a child - it is the parents' responsibility to support their offspring at least until they are 16, and in many cases for longer. The most that is usually expected of the children is that they become financially independent and can act as an emotional prop in the parents' old age. Given that this is the primary reason for having children in Britain, it is probably reasonable to expect that most are cared for and loved in a particular way. In other countries, however, children are seen to serve a very different purpose. Much of China's population still lives in rural communities, where backward economic conditions, and the old traditions and cultural norms which these nourish, still apply.
Rural society is based around large farms, where the extended family lives and works.
The survival of these farms depends on large numbers of children to work the land. Only in urban areas, where the birth of a child is more likely to bring expense than income, does it make sense for couples to have small families. Orphaned or unwanted children, who are sources of security for nobody, are unlikely to be seen as anything other than a burden. If it is possible to understand why children are viewed differently in China to the way they are over here, it is possible to appreciate too that the Chinese tradition of boy-preference has a real basis in that society. The rural farming community is structured around extended families.