Maybe because you never stop campaigning.
Via Weekly Standard:
At a stop in San Francisco on a three-day fund raising swing along the West Coast, President Obama said during a speech that “sometimes people forget I’m not running for office again.” The president was talking about Republicans in Congress and the immigration reform that he is trying to get through the House:
And some of them even forget that I’m — sometimes people forget I’m not running for office again. Michelle doesn’t forget. (Laughter and applause.) So you don’t have to worry about this somehow being good for me. This is good for the country. It’s the right thing to do for the American people.