Because it doesn't make any sense. Amazon doesn't dominate the jobs market.
If you live in such a place and Amazon is your employer, it may well be the case that you don't have a lot of other options, especially if what you came from was being on social assistance.
If they do their research, they'll realize they probably won't have a job for that long [1] and it would be preferable to stay in a position (that likely pays better with your examples) that is reliable.
[1] https://www.ibtimes.com/amazoncom-has-second-highest-employe...