Both Clinton and Bush were aware of what proper behavior was. Obama is only aware of how he has to behave in order to get what he wants.
Now that he has the Presidency, he knows that he could unzip his fly in the middle of a press conference, piss all over the front row of reporters, and they would have to figure out how to spin it in a positive manner.
Clinton aware of proper behavior? ROTF!!!
That's practically what he's been doing. He has not allowed a single real press conference since he came into office. He treats the press corps like a bunch of pests. He has repeatedly excluded them from important events. He just skipped the annual dinner this weekend. And he hasn't even invited them for cocktails or thrown them an ord'oeuvre, the way clinton did. He has weekly parties, and the media are not welcome. It just goes on and on.