Why are Requisitions and POs disconnected from non-stock, Inventory Items on Sales Orders?

We are a distributor who is implementing Order Management to replace another application. We have <1000 items that we stock and 90% of our sales are non-stock items that we require be shipped to our facility before being shipped to the customer due to the nature of our business. When we set up these "non-stock" items, we set them up with INVENTORY_ITEM_FLAG = 'Y' but do not put a min/max values so that when the requisition is built from the Sales Order IN_DEMAND lines, it will always be a requisition. However, when those items are passed from