Because, according to the WaPo's Dana Milbank:
...President Obama has many talents, but he is not good copy. He speaks grammatically, in fully formed paragraphs. He has yet to produce a scandal of any magnitude. He is maddeningly on message, and his few gaffes — “you didn’t build that,” “the private sector is doing fine” — are inflammatory only out of context. If it weren’t for the occasional relief offered by Joe Biden, the Samaritans would have installed a suicide-prevention hotline in the White House press room by now...
As for Mr. Romney, well....
...At these times of declining revenue, we in the media need to stay true to our core interests. As the old saying goes, we should “vote the story.” And the better story in this election is clearly President Romney.
Romney’s hit parade — insulting the British, inviting Clint Eastwood to the Republican convention, flubbing Libya and now dismissing half the nation as parasites — may make good copy for the next seven weeks. But if we go easy on the man, we could have four years of gaffes instead of just seven more weeks. Admittedly, this may not be the best outcome for the country, or for the world. But in this race, there is no denying that one man will give us much better material...