In the ever splintering cultural landscape of American politics, politicians believe it is their right not to talk to press they don't like or answer questions they find difficult. Sarah Palin essentially set the precedent for this behavior after joining McCain on the Republican presidential ticket in '08, failing so miserably in her initial exposure to the media that she then refused to hold a press conference or engage in hardball interviews ever again.
Now we have mindbendingly ignorant products of the bible belt like Michele Bachmann and Christine O'Donnell parading themselves as politicians, again refusing to engage with the 'enemy' (ie. the liberal press). Just watch Christine O'Donnell's ridiculous reaction to Piers Morgan asking her questions about topics she wrote about in her book:
At some point this game has to stop - politicians have a duty to answer questions regardless of where they come from or what they are about. After all, they receive a salary from the tax payer and their duty is to them, not their careers.