The order ID field is conducive because it places all of the items that the customers want under one order. You can imagine how problematic it would be if the rules would be set in different areas. It will be harder for the company to track the orders of each customer.
This may lead to people receiving items that they did not order or not getting any of the things that they have ordered at all. The order ID field will make everything more organized and correct. The fewer mistakes that the company makes in processing orders, the happier the customers will be with their shopping experience.