Remember this? As the photo above will helpfully remind you, Hillary tried one of the more absurd dodges of her life back in July when she said she wouldn't reveal her position on the Keystone XL pipeline until she became president. The faces of her purported fans furled in disgust and confusion as Hillary tried this one on for size: "I am not going to second guess (Obama) because I was in a position to set this in motion. I want to wait and see what he and Secretary Kerry decide."
So because she "set this in motion" as Secretary of State, meaning the first four years of foot-dragging in the review process were under her watch, she felt she had a special responsibility to say nothing. I suppose that would include saying nothing about why, after four years, she couldn't make a decision and handed it off to Kerry to do more foot-dragging.