Some of you might already have home delivery in your local area using the inventory you have in-stock in your store, and want to continue to use it where possible via your online store.
With your online store, it may make a lot of sense for you to delivery orders that are made up of products you have in stock from your store inventory, rather than through Endless Aisles. For example, shipping through Endless Aisles can cost $9+, while putting an order in an Uber, or dropping it off on your way home could be a lot more economical. Additionally, you'll be able to offer same day delivery vs. the 1-3 days that is offered through Endless Aisles.
With Shopify, you can manually process received orders to tell Shopify how to split the orders up between your store's fulfillment vs. Endless Aisles fulfillment. If you don't want to do this yourself, this service is included with the Pet Store Websites subscription in the form of an e-commerce administrator.