In times of relative peace, it's less expensive to store things in a centralized, more secure area.

Items like first aid supplies, munitions, food, water, communications equipment, gas masks, tend to grow legs and wander away, when scattered in a bunch of different locations. However, if you're expecting these supplies to get used soon, and want them to be there for any of your citizens to use, be they military or civilian, you go ahead and disperse them.

Could also be a drill or training of some kind, who knows.