Knowing the popularity of each of your products within the near future gives you the opportunity to optimize your warehouse and your  (costs of) storage. High demand products will be ordered frequently and should be stored in a place that is easy to reach. On the other hand, products that will be less popular in the upcoming period will not be ordered a lot and can be placed in the back of your warehouse. Also, knowing the approximate demand for each product allows you to manage your inventory well. This prevents over- or understocking.