There are many explanations companies routinely give when inventory management issues arise, whether it's too much unsold inventory or too many empty shelves.
"The market is unpredictable."
"It's impossible to accurately forecast everything."
It's not that these explanations are inaccurate. In fact, they're pretty much universally true. What's puzzling is that, despite these realities, brand manufacturers still pour all their energy into rigorous planning and forecasting, and yet take a more frenzied approach to responding when performance deviates from forecast. In other words, they lose the discipline they need for a fast, coordinated response in the face of changing demand.