This is more or less how it should be. If Amazon isn't going to offer a good enough deal, then companies shouldn't move packages for them. As more and more people figure it out, other delivery companies will stop working with Amazon as well, although it may be that the deals work out better in places with lower cost-of-living, easier delivery routes (due to climate, geography, etc.), or other advantages. If some othe…
Or Amazon can just buy them and make it work.
Amazon outsources the insurance, health, org, and most of the business risk to these sole supplier contractors. They can choke them to death and just say, "Welp, time to fund another one" until they get the results they want.
Only Amazon can determine which results are acceptable due to these arrangements.