Ecoperson I have to disagree with you about people having far more reasons to leave their hometown that to stay. You'll find plenty of research supporting the fact that Americans aren't all that mobile despite what we believe. According to an article from the NYT:
"Over all, the median distance Americans live from their mother is 18 miles, and only 20 percent live more than a couple of hours’ drive from their parents."
The popular perception of Americans is that they are independent and rootless, but the reality is that people tend not to move very far from their parents.
www.nytimes.com
68% of Minnesotans were born in Minnesota. There is a strong draw to stay put or to return home. That is just one of the advantages of in-state recruiting. The other is the time it takes to evaluate players and having more information from coaches with which you have a relationship. Evaluating players is hard...if it weren't all those scouts in the NBA would get it right every time but even they don't even come close and they have a lot more info that a college coach does.