Some students have been admitted to the doctor's degree, but they have begun to be lazy. They think graduation is a piece of cake, and they gradually begin to hate learning. I don't usually work hard, so I missed a lot of classes throughout the semester. According to the attendance sheet, this person doesn't come to class too often, and the school has the right to expel him. Because colleges and universities don't invite doctors to eat, drink and have fun all day, but come to the school to do academic work, it is best to win glory for the school with an award. The school gave the doctor the best educational resources and followed the famous professors to do research. If students don't work hard and have no mind to study at all, wouldn't this excellent place of school be wasted? I gave you the opportunity to further your studies, but you didn't cherish it yourself, so you just quit.
There are also many people who failed the exam. Failure to pass the exam means that you haven't worked hard, or that you don't have the talent and ability to study this major, so there is no need for you to continue studying. The reason why the school dismissed you is that you want to go out and find another way out as soon as possible, instead of wasting your time in this university under the name of a doctoral student.
There is plagiarism. This kind of behavior is anathema to colleges and universities. If you plagiarize or cheat in the exam, it not only shows that you have no learning ability, but also shows that this person has ulterior motives. Why does the school spend a lot of time and energy to train a student with personality problems? Even if you have a superior IQ, if you can't be a man, you will be completely denied.
The others didn't behave well. Some doctoral students do evil in or out of school and break the law, which is absolutely intolerable to the school. Such people will also retire directly.