Why do some people not want to come back after studying abroad?

In recent years, 400,000-500,000 people have gone abroad to study, and 400,000-500,000 people have returned from overseas every year. Only a few thousand people can really take root after studying there. In short, if you want him to come back, he won't come back, because he can live well there (this kind only accounts for a very small number of international students); If you don't want him to come back, he will come back, because his life there is very difficult (this is the vast majority of international students). Nowadays, most of the international students (except those who graduated from top universities such as the resumption of diplomatic relations in North China and went to world-class universities such as Europe and the United States) can't get into good universities in China, and a large part of them can't even get into high school, and their families have money. These international students can't compare with those in the 1980s. At that time, the state sent the best young students to study abroad for free. At first, only 500 students were sent, and then thousands were sent a year. Now there are more than 500 thousand people studying abroad for one year. Among them, excellent students are few and far between, with the overall ratio less than 10000, and most of them are scum. Most of them are people who can't get into high school or a good high school or a good university. Such international students have poor learning ability and self-management ability, can't stand suffering and injustice, and spend a lot of money at home, whether abroad or at home.