For me personally, my parents were just following a "trend".
One major reason for studying abroad is the recognition the school's get. Many chinese universities aren't recognized (or aren't placed as highly) as foreign schools so people go to those schools in order to have a better chance of joining certain companies. For example, medical school In china isn't accepted in Canada and the states (so learning med in china means you can't be a doctor in NA). Also, many people I know study both abroad at a top school, like UofT, Ivey, Cambridge etc and also at a prestigious school in China in order to get that extra bump for their resumes. This usually allows them to more easily get executive positions at companies. (especially foreign companies who have a china branch. That's what one of my cousins did.)
Another reason is quality of education, although Top chinese universities have really good education now, middle tier universities just aren't that great compared to middle tier foreign universities. So often times wealthy familes will send their children abroad because they couldn't make the top chinese universities.
Also, it's a status symbol to a certain degree. Many people take pride in being an international student (But it can't be a third rate uni, that would just be dumb)
Furthermore, going abroad is a great way to make connections and to improve your English skills (or whatever language), which is really important in business. This is also partly why I went abroad, to improve my English (which no lie, has gotten so bad over the past few months...)
And then you've got the cases of families moving money through the student. But this has been really difficult to do now because of all the regulations and investigating.
But honestly, often these are failed investments. Spending hundreds of thousands on studying abroad to graduating and only making ¥4000 a month back in china. Really unfortunate. So, I guess many people just go abroad for the experience.