Coaches have no issue getting rid of a player if they can find someone better, and even less of an issue leaving for a better job. Why should a player be stuck in his situation if he's not happy, or could have a better opportunity elsewhere?
The answer to your question is an opportunity for what?
Without taking a stance on how anything "should" be, let's take a dispassionate view of things.
A kid attends a high school based on where they live. They are there for an education. Sports, clubs, etc are
extra-curricular activities. If the basketball coach or the key-club advisor leaves/retires, the kid still gets an education at the same school. Certainly, there are exceptions with recruiting to catholic schools, etc, but by and large, sports are "extra" to the education.
Why is college different?
Historically, a kid decided to attend the university AND play sports. A kid was free to leave and seek their education elsewhere, but there were some controls(ie waiting year) imposed by the NCAA over sports to govern competition to prevent chaos and a primary focus on sports vs education, which was/(is?) the primary purpose of a university.
Let's be honest. Penn State is a good school. Graduates of PSU generally do well with a "name brand" and respected degree. From an education perspective, there was no reason to leave, and most of the transfers will likely go to a lesser-ranked academic institution. The mass transfers, in the wake of shrewsberry leaving are simply more evidence that for athletes, sports is not an extra-curricular, education is an extra-athletic.
It's obvious to me that sports has outgrown education and they should probably be decoupled, unless we want to say that universities are minor-league sport entities that have a secondary role to offer education services.