I believe that they are doing this, but it seems kind of impractical to me honestly. Then again amazon is able to operate without turning a profit so i guess they can enter in these peripheral branches if need be...
I'd imagine that having Amazon Fresh trucks driving around a neighborhood with a local fulfillment center could easily turn into their own solution. Combine this with Amazon Locker and 20 years from now Amazon drone and good bye UPS.
Amazon Lockers have been a boon for me living in apartments with hours that don't match up to my schedule for their 'helpful' package signing service. I recently noticed I can return packages through the lockers as well. If they can saturate with enough lockers I'm not sure I'd ever actually need the "final mile" of an actual delivery service.