The airports may be open but they are restricting landing/take off times heavily. Their runways are in terrible shape not to mention the aprons. Also many of the staff are unable to leave their homes to even get to work. And the weather still isn't all that great.
As far as cancelling flights to try and operate one full one, whoever it was (can't remember) that said planes and crews all had to be somewhere is correct. We don't just cancel on a whim. Many times downline stations are experiencing air traffic concerns and cancel an airline's landing slot. When that happens we have no choice but to cancel a flight, get everyone out on another and use the slot that has been left for us to accomodate that flight. Flight attendents, pilots and even the airplane all have schedules and are expected somewhere else so to cancel a flight often means a plane has to be ferried to continue it's schedule or another one rerouted.
Happy and safe travels!