University is a small society,
Everyone in high school works hard, takes money from home, and has no interest in communication. It's easy to get along with playing.
As for universities, going to the society in the future may be competitors, or there may be no more contacts. Who knows, there is a lot of potential competition.
Moreover, many students are leaving their parents for the first time, and their small temper has not yet been honed. Premature contact with society will only make it harder for them to survive. Obtaining a certificate is one reason. If there is any other reason, it should be this.
For many people, the university is just a buffer zone. After this buffer zone, you can adapt, think about it, and then you can leave. Start your own business and go your own way. This is not life.