Why not? What are you hiding?
That's easy. Obama is hiding the fact that he's a stupid jackass who only went to college because of Affirmative Action admission policies and Affirmative Action free-money Scholarships.
He's hiding the fact that his grades are horrible, and demonstrate that he's a simple minded fool who never should have graduated, let alone gotten anywhere in life.
Rest assured, if Obama's grades were any good, they would have been pushed in our faces constantly over the last 8 years. His grades are horrible because he's an idiot.