Fulfillment operations is not just delivery to the customer, or owning the warehouse. All the employees that work in the warehouse, move stuff from warehouse to warehouse or warehouse to store, are all part of fulfillment.

Amazon does not deliver to customers. They pay separate businesses (they call them delivery service partners) to deliver to customers:

https://hiring.amazon.com/job-opportunities/delivery-driver-...

https://logistics.amazon.com/

FedEx does the same thing with FedEx Ground:

https://www.buildagroundbiz.com/