First of all, the westerners have a different consumption concept from that of the Chinese. They will buy anything they want and can afford without hesitation. While for the Chinese, they will think over before buying a commodity and may decide not to buy it, especially for the goods that are not so necessary for them.
Secondly, the westerners have a higher living standard than the Chinese do. As we know, the western countries such as America, British, France, etc. are more developed than China, and they have better social warfare than China accordingly. For this reason, the people who live in these countries can afford most of the goods and don't care how much they cost. However, most of the Chinese may have to support their parents, raise their children, and pay for the house rental and so on with their little salary. So they dare not to be so arbitrary in consumption.
The last but not the least, the westerners pay more attention to eye protection than the Chinese do. They have a clear classification on the functions of eyeglasses. Going outside needs a pair of sunglasses, reading needs reading glasses, surfing on the internet needs computer glasses, doing sports needs sports glasses...Different kinds of glasses have different functions, so that they can protect their eyes better. But the Chinese usually have only one pair of glasses mainly for vision correction. They think one pair of glasses is adequate enough to meet their needs.
The above points can account for why the westerners usually have more pairs of glasses than the Chinese do.