Considering that Obama was elected President and none of his predecessors had this requirement thrust upon him, the question isn't "why can't he," rather "why should he?"
In nearly all cases it isn’t necessary. Go back the last 50 years. How many times has it come up? Once with Obama, and once with McCain - about whom I have my doubts.
In fact it has happened several times, but in the overall scheme of things, it doesn’t come up that often. Most people running for POTUS have solid American roots which don’t require proof of citizenship. George W Bush for example. George H.W. Bush, Ronald Reagan. Jimmy Carter. Gerald Ford, Richard Nixon, JFK, Lindon Johnson, Eisenhower, Hoover.... In fact you have to go back quite a ways to find an unconstitutional President based solely upon the Dual citizenship issue. That person was Chester Arthur who became POTUS because of Assassination. His father did not become a Naturalized citizen until 14 years after Chester Arthur was born, also making Arthur ineligible because of Dual Citizenship. The difference is.... NO ONE KNEW ABOUT THAT until 2009. In Obama’s case, we know about it NOW.
The only difference is this, No one knew that Chester’s Dad wasn’t a Naturalized citizen at the time of his birth. He did become one, and at the time Arthur was elected VP, he was of course a citizen. But not when his son was born. So Chester had dual Citizenship. Obama’s dad never becane any sort of citizen of the United States, he died Britisn and kenyan. Obama’s son was born , British, Kenyan and American. His Kenyan citizenship expired in the 80’s
The whole house of Obama cards lay on a foundation which states, “it doesn’t matter who your parents are or what their citizenship is, if you were born in the USA, then you are an NBC.” This is patently false. It is nothing short of a lie, and Obama and many others are relying on enough people believing this lie through continued IGNORANCE. Ignorance to what a Natural Born Citizen is and isn’t. Natural Born Citizenship is RESERVED for those who are born to parents who themselves are citizens, and born upon the soil of that Nation. If any of these details is not exactly that, then the child is not a Natural Born Citizen.
Obama is a Cretin and an Usurper. Whats more, he KNOWS it, and is counting on the ignorance of the American public in order to keep power.
Take that ignorance our from under Obama’s foundation, and his whole house of cards comes tumbling down.