> If it was that bad, I think they'd have a harder time hiring.
You're severely underestimating the punishing conditions of an Amazon warehouse job.
A picker has a tablet that alerts them of an item to get. A clock starts counting down on the time you have to get to the right bin, find the item, and scan it. The warehouse sorting algorithms created by Amazon engineers optimize for retrieval time - but the warehouses are so huge, this means in practice that you have exactly as much time as you need assuming you never stop moving. For your entire 8-9 hour shift.
A typical amazon warehouse worker is essentially powerwalking non-stop for 8 hours straight on hard concrete floors. Breaks begin at a scheduled time, but your break begins when you sign out of your device, then you walk some distance to the break room (typically a 3-5 minute walk), AND you have to be signing back in to your device at the end of your break time. In practice this means your actual resting time on break is typically 5 minutes or less for 15's, 15-20 minutes for lunch. You are not allowed to sit or rest anywhere other than the break room.
If you sign back in only a few seconds late from your break, a manager will speak with you about it. If you sign back in 30 seconds late a few times in a row, you can be fired.
It's true that Amazon pays well in the warehouse space and is constantly hiring people with no experience. However, this isn't because Amazon is a great place to work - it's because there is an incredible amount of churn. People burn out of Amazon warehouse work constantly.
If you search on google for Amazon warehouse stories, you'll find a lot of people talking about how physically punishing the job is, about the constant stress from 22-year-old "managers" doing their rotation through a warehouse and enforcing Amazon's draconian rulebook without a thought in their head about the people they're taking to task for coming back from lunch 30 seconds late.
There's a blog out there from a guy who worked in Amazon warehouses in the Midwest, who documented everything while looking into trying to organize. The stories he tells about the work environment are hair-raising.
Amazon has figured out how to optimize the physical output of a human being, squeezing every last ounce of productivity from them every second of a shift until they either quit from burnout or get fired for not "making rate" (total % of lateness picking or packing assigned items). The fact that Amazon has an endless supply of people signing up to work in this environment says less about Amazon and more about the state of the American economy and how many desperate people are out there who need to sell their physical and mental health to Bezos pay their bills.