The argument is usually that university resources were used (wifi, computers, space, etc), so the university should receive compensation since tuition is to pay for receiving an education, not starting a business.
Having said that, schools that still enforce a policy like that are only hurting themselves by discouraging entrepreneurship, and it's only a matter of time until all schools have similar IP policies as this one. I'm lucky my university strongly believes in encouraging entrepreneurship and does not assert any ownership over student work, even if university equipment is used.
since tuition is to pay for receiving an education, not starting a business
I think there is a gaping hole in this argument. When you go to a college/university, you are entering an environment of learning and exploration, both personal and intellectual. It's not just an "education" in the sense of "book knowledge." Some unis have policies dictating where you can live, whether or not you can drive a car, and have disciplinary policies for violating certain rules (read: drinking) that have to do with this environment, not with intellectual education.
And I completely agree with you that schools that try to get it both ways and deny the student the fruit of their complete growth, including entrepreneurship, are doing them a disservice.
Do athletes that turn pro based on the skills they develop in college have to tithe their salary back to the school?
EDIT: I obviously need to make it clear that I am continuing your point, not disagreeing.
Having said that, schools that still enforce a policy like that are only hurting themselves by discouraging entrepreneurship, and it's only a matter of time until all schools have similar IP policies as this one. I'm lucky my university strongly believes in encouraging entrepreneurship and does not assert any ownership over student work, even if university equipment is used.