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170 posts later this question remains unreplied to ...
Because the answer is self-evident to most people who understand the adversarial nature of politics?
Many birthers want to remove him from office and/or seen him in jail. When he is under no legal obligation to provide the information birthers are demanding, why would would he voluntarily comply with his sworn political enemies?
Birthers only real hope at this point is finding a sympathetic congressman...good luck.