An oddity of politics is that one has to be open and encompassing, quite literally have a million close friends, in order to get elected. Once elected, the cacophony of all those friends mixes with the complexity of the job to make a totally unbearable mishmash. It doesn't matter if you are a small town councilman or President of the United States, the natural reaction is to try to shut out as much of the noise as possible. Since you can't make the job less complex you start limiting the number of voices you hear.
It is perfectly natural and also incredibly stupid.
Also natural is that your closest aides will encourage you in this self-destructive behavior because they realize that their personal power over you is inversely related to how many people have your ear. If your inner circle is five close advisors and you suddenly decided to increase that circle to 25 then their power diminishes greatly. Your inner circle will naturally fight like rabid animals to keep that circle as small as possible.
Such is the case with President Barack Obama. In my lifetime I don't recall any president who successfully bucked the inertia of their aides to cut them off from their greater network of friends. My gut tells me that Eisenhower and FDR managed it - Ike because he had long experience with headstrong assholes during WWII and Roosevelt because his personality was too strong to be locked away either by polio or advisors. My gut says this but I can't be certain. All the presidents of my lifetime (Clinton, Bush I & II, Reagan, Carter, Nixon, Johnson) ignored their cabinets and allowed access to only a very small circle of advisors.
More recent presidents have had the likes of Rahm Emanuel and Karl Rove. These aides set themselves up as high priests, the only ones allowed direct access to the President. All the others must submit their petitions through the priesthood. It's a bad way to run a life and a worse way to run a country. Still, I understand why it happens. It's human nature.