Fedex mentions this is not a material amount of business. How Amazon operates it's last mile logistical network is unsustainable. These people will eventually churn out of the open air sweatshop that is delivering last mile for Amazon (Fedex's requirements are much less onerous on the ground/home delivery side, based on my conversations with both Amazon delivery drivers and Fedex ground and home delivery drivers).

Very similar to the high churn Uber and Lyft experience with drivers. It lasts only as long as you can find people desperate enough to work in these roles.