Because college admission (college entrance examination) is not fair, but the result of the balance of interests in various places.
The crux of the problem here is that no one actually puts fairness first, but balance first, such as taking care of remote areas, taking care of ethnic minorities, taking care of local students and so on. From the perspective of system design, this is actually a very obvious thing.
This system has its reasons for existence, but obviously this system does not take fairness as the primary consideration!
The root of the tragedy is that all students from small to large have been instilled with a theory of educational equity, that is, as long as you work hard to get good grades, you can go to a good school, receive a better education and create a more brilliant life.
Before the college entrance examination, this view is generally not wrong. After all, in most parts of China, except primary schools, admission to junior high schools and senior high schools is almost absolutely fair (regardless of hidden rules). Mainly because junior high school enrollment is generally based on household registration, but within the scope of a city, county or even a province, the conflict of interests between regions is not particularly prominent.