I believe the real reason President Obama doesn't want to be on the Supreme Court because a future President could do to him what he did to the Supremes during the SOTU address in 2010 over Citizens United. Obama wouldn't want to be in a position where he would have to sit there and take it like the Supremes did save for Sam Alito.
Besides he would be but one out of nine rather than the center of the world's attention. You don't get much more center of attention than if you reside at 1600 Pennsylvania Avenue. Yet this has come to be boring for him. If he's bored by the Presidency, a tenure on the Supreme Court would be tantamount to a death sentence.