But those athletes became famous and successful precisely because they were allowed to leave and pursue their dreams - had they been stuck in their hometowns they wouldn't have achieved anything of the same caliber. If it's okay to leave your hometown, why isn't it okay to leave your home country?
The notion that people are beholden to the country they're born in is absolutely braindead. You're basically saying that a person born in a gutter should stay in that gutter because the gutter might benefit from it.