The fundamental reason for eating is that the lips will not be closed when eating. The sound of teeth biting and mouth sucking are completely different. You can play down the sound of eating a potato chip when your lips are not closed and the sound of eating a potato chip when your lips are closed through mobile phone recording. Compare and listen to it and you will understand. Some people have a habit of eating and mouthing since childhood, and no one has corrected it. Since childhood, they have accepted the concept of eating and mouthing. Subconsciously, they must express their delicious food by mouthing. When eating and chewing, their lips are closed, and they can be eliminated after eating. Eating and mouthing is caused by personal living habits and environment, and eating without mouthing is also caused by personal living habits and environment. Some people may say that there is no time for you to eat slowly. Sometimes some people will lose some important interests related to themselves because of their own eating, and some people will correct them. I don't object to eating. When people are very hungry, it is inevitable to eat quickly. Let nature take its course. Basically, it is caused by the living environment. At first, my lips won't close when eating, so I want to eat faster and eat more than others. Later, it became the concept of eating faster and eating more delicious.