What are some typical reasons why employees quit their jobs?

Changing the ownership of the company is also to push people leave their job.

I've been working with some people who doesn't really know what they want in their career road map and therefore become a job -hopper. They work here with you, then suddenly see a friend who can make more money in other industry, hence they can decide to switch job just simple like that. i must say I take certain responsibility when recruiting them. I now make the interview process very strict and focus to ask a lot of orientation question like:
- What do you want to become in the next 3-5 yr
- Why you think this job fit w that future?
- How do you think if friend at the same age can make more money, higher position next year?

90% candidates are get a new job 'cause the enviroment and 10% for the boss but when they leave, that's else

Just curious, is there any well researched data on why emplyees quit their jobs?

Một trong những lý do sâu sắc nhân sự việt nam hay nghỉ đó là bản thân nhân sự chưa đánh giá đúng mình là ai - năng lực mình thế nào - mình đã tận tâm cống hiến cho công ty chưa- mình đã vượt qua khó khăn trong công ty chưa

hay nói cách khác mình đã " cho " hơn là đòi hỏi " nhận " từ công ty chưa