There is a parallel here in the American experience with foreign students. After 9/11, American policy towards students from abroad and student visas became harsher and more restrictive. This resulted in a redirection of students to places like Canada and Germany. Now, we're seeing the flip side of this.
Students that would have maybe studied in America are finding themselves leaving Germany as soon as their education is completed, due in large part to the complexity and difficulty of complying with restrictive, anti-immigrant laws that discourage keeping intellectual capital in the country. Germany needs foreign workers, desperately, in order to maintain its status as a net exporter of goods. It is not uncommon for one German worker to support as many as five other individuals (extended family, etc.) and it is entirely possible to do that here.
If you are going to bring people to your country and educate them and provide them skills, keeping them should be easy. Instead, these people, who have great value and potential, move on, looking for something palatable. Who can blame them?