In my mid-20s, before I went back to college, I worked in a grocery chain's fulfillment warehouse. The conditions were absolutely inhuman, it was a back-breaking job. Management made it worse by re-timing all of the performance goals to lower our pay. You had 8 seconds per location for picking and a short amount of travel time in between. That 8 seconds might be a few cases of toilet paper, or 250lbs of dog food. Then they would do things like trot out a "ringer", generally a long-time employee who had been promoted past picking to something higher-paying such as forklift operator. Then they would have this ringer do cherry-picked routes for a day, post the list of the week's performers, and claim that the rest of us weren't working hard enough.
I know people who worked in Amazon's warehouse. The conditions there are just as bad if not worse. Oh, and get injured (not unlikely given just how physical the job is, and the long hours)? Get a lawyer, if you can afford it. Amazon will go to any length to fire you before they see you collect a dime in worker's comp.
When you see Amazon's market share grow and grow, remember that it does so on the mistreatment of others. They should find another job? Not likely. These warehouses are usually placed in rural or disadvantaged areas where there are few employers.