Why do window shutters need to be up for a plane to take off?

Window shutters on an airplane are in the up position at take off for safety reasons. Having the shutters open provides the crew as well as the passengers the ability to spot any potential dangers outside the aircraft.

On a related note, having the window shutters in an up and open position at the time of take off permits rescue workers and others the ability to see inside the plane, at least to some degree, in the event of an emergency. The same window shutter protocol is used at the time of landing as well. Statistically, take off and landing represent the two points in time when emergency situations arise.