I absolutely love Amazon's Locker service. It only works in large urban areas, but it allows them to cut out much of those last-mile costs. I hope it's working for them.
But Amazon Locker deliveries aren't any cheaper or faster than normal Prime deliveries, at least when I looked into it a year or so ago in San Francisco. The only use case as far as I could tell was you could have things delivered there if you don't have a secure place at home for packages to be dropped.
And they're not the only one deploying lockers. The integer.pl group is starting to invest hundred of millions of dollars to installing 10k+ lockers worldwide.
This is will be integrated with amazon's warehouse robots.