Have control over your Products
With other online retail channels such as Ebay or Amazon, you as the supplier lose control of how your products are marketed and priced online. This can result in your products being sold at prices that your current brick and mortar stores can't sell it for, so eventually you will lose your brick and mortar store sales. It is possible for online shop owners to make a 10% profit, but for retail stores it is not possible to make a 10% profit and stay in business.
