Perhaps because Joo Hee-jung dropped out of college, he seems to place a high value on a diploma..

In the early stages of his career, there were rumors that he preferred going pro early, and he later became more open to the idea. However, seeing him emphasize in interviews that he is the only player from his Korea University cohort to actually obtain a Physical Education degree, it seems he still values having a KU diploma over going pro early..
While a degree is necessary to consider life after retirement, since re-enrollment is possible later, it would seem more logical to go pro early if the opportunity arises. But perhaps because of his own experiences, Joo Hee-jung seems to prioritize receiving his degree on schedule..