They are now competing with robots for the available positions. We are entering an era in which no humans need apply.
Robots cost money, of course. Such advanced electronic devices do not come free. Amazon was surely aware of this fact when it purchased Kiva Systems. Which is why they bought the robotics firm. When you own a manufacturer, you've cut out one middleman who gets a slice of the financial pie. That's an extra piece for you.
Investment in robotics won't pay off for Amazon this quarter, but in time the robots scooting about the warehouse picking orders will pay for themselves.
Because robots don't need breaks, they can be run continuously for extended hours before powering down for maintenance. No robots will be seen at the outer door with a ciggie and a cup of coffee, wasting time. The robots don't break for lunch, either. They just keep scooting up and down the aisles in the warehouse, taking what is requested and delivering it to the packing machine.
The modernized Amazon warehouse needs a few human bodies to manage the robots, but the warehouse had human managers managing the humans before robotics were introduced. The order pickers are gone, and those jobs are gone as well.
Shelves are arranged for the convenience of the machines, with narrow aisles that allow for a larger stock to be held on hand. The machines go faster than people, and as long as the items are where they are supposed to be, the machine can't pick the wrong thing. The robots won't be showing up for work hung over from a party the night before, either.
The robots can carry more weight and move faster, which speeds up the order processing and allows for more material to be shipped per day. To achieve the same level of production, Amazon would have to hire a small army of humans. That sort of mass seasonal hiring is a thing of the past.
We have arrived at Huxley's Brave New World, where machines do the work and people sit around smoking marijuana---isn't that our version of the author's "Soma" drug that calmed the masses?
What will society do with all those who need work but are pushed out by machines?