If they had followed their parents back then, Chu Weixu would have surely stayed abroad to study until he worked for a long period; or even worse, Chu Weixu wouldn't be allowed to return for the sake of his future, and his family strictly prevented him from falling into the same love affairs.
While Ai Zhiyi, would only be in that country for the rest of his life; waiting for something that would most likely never happen to happen until he got tired and died.
If they ever had the chance to meet again one day, it would be in the most heartbreaking moment for them where one of them felt so downhearted and the other one was deeply frustrated by the pressures. Or the worst of all, both of them were married and got numb to each other, so their meeting was simply a reunion of old friends.
If they followed their parents, then all of that could happen, or even worse.
