Why would you limit your sales to only one channel and be invisible to users on other channels?

One of our clients, Rainvac, had been using an OpenCart e-commerce platform for some years. But he wanted to sell his product line on Amazon, e-Bay, and Overstock as well. However, he wanted to use the OpenCart platform for fulfillment of all his orders. Hence, we used Amazon, e-Bay, Overstock web services/webhooks etc. to sync the orders and shipping information in real time with Overstock. This has enabled the client to administer one platform only while selling his products on multiple platforms.