That seems like a simple money regulations issue. If the school has a $100 million endowment, but doesn't spend into it, the school would exist forever. If we say 10% returns a year, that's $10 million to spend on students in the form of teachers and classrooms and housing and books and everything. Unfortunately, that only teaches N students per year. But it would last ~forever. If, however, you get greedy with wanting to teach more than N students per year, then you get into the treadmill of needing external funding forever, but on the face of it, I don't accept that external funding is required forever.