why do you assume that someone is exerting pressure? NPR and NYT are very much "establishment" media outlets that have deep dependence on the government unilaterally from their side.

But the more important point is: the snowden revelations are dangerous to their status quo (if only marginally so). It takes incredible willpower and self-discipline to fight the natural reaction to do anything but think about whatever is threatening to upend the reality that you are comfortable with. This is often true even if the new reality stands to your benefit.

There's no need for the government to exert pressure for this to be happening.