Teeth are messy and ugly, and it's not easy to keep them clean, but many Japanese think young people with messy teeth are cute, so some parents also think that their children don't need to have their teeth corrected. This is a cultural difference.
Another reason is that Japanese food is changing. Before Japan's rapid economic growth, Japanese people seldom ate meat or animal protein. At that time, the staple food was rice, and the vegetables were vegetables, seaweed and tofu. However, Japanese jawbones are relatively large and have a strong bite force. Modern people seldom eat hard food, and as a result, the jawbone is getting smaller and smaller, but the size and number of teeth are the same as before, so the jawbone can't put away the teeth neatly.
Moreover, the cost of orthodontics in Japan is quite expensive, which is not a small sum for the general public. Moreover, orthodontics is also related to the skull. It is more difficult for Japanese to correct their teeth, because most of them have small maxilla and large plane angle of mandible, and the bones of orientals are harder than those of westerners. These factors invisibly increase the difficulty of orthodontics.
There is also a saying from a professor at Osaka University:
Japanese people have irregular teeth because they eat meat instead of bones. After studying the living habits of the two countries, the professor began to understand. The original problem is that people in China have the habit of eating bones while eating meat. Braised pork ribs, rock sugar elbows, these typical Chinese dishes all need to "chew bones". Even overseas, China people with a conservative diet still keep the habit of eating meat with bones. From a medical point of view, things are easy to explain. Because children chew bones, their gums will be strongly squeezed. This kind of squeezing is a benign stimulus to the gums, which can force the gums to grow fully, and the teeth will grow neat after changing teeth.
Finally, Professor Semura used a knife to describe the teeth that have eaten bones and the teeth that have not eaten bones. He said that China people have sharp and beautiful teeth because they often chew bones, just like sharpening a knife; Japanese teeth, because they don't chew bones, are like knives rusted in their sheaths, and no matter what the texture is, they can't function.
This kind of problem brought great trouble to the Japanese during the Second World War. When they selected pilots, more than half of them were eliminated because of uneven teeth. If the teeth are uneven, you can't bite the oxygen mask tightly and you can't be a pilot. Professor Raimura believes that this congenital defect restricted the quantity and quality of Japanese pilots, so they were defeated by the allied forces in World War II.