Running an eCommerce business has its ups and downs. There is nothing like the thrill of knowing that your products have arrived at your customer’s doorstep in one piece. While you can probably handle delivery and shipping by yourself when your company is starting out, the need for a reliable logistics provider arises as your company expands. 
You might argue that you have better control of the delivery process while the operations stay under your business, but you have more room for exploration and less for risk and high costs when you find a reliable logistics provider. Think about it. 
When you outsource the work to another company, you won’t need to spend as much on delivery and shipping. You can expand your product range, and if there’s a loss, you let them take it on. You can even look into international shipping with a 3PL provider. 
https://www.entrepreneurshipsecret.com/third-party-logistics-providers/