As far as I can see from a literal 5 second google search:
- Liability for Injury at work is no longer on Amazon
- Liability for injuries caused by Amazon workers get shifted to the Worker, rather than Amazon (despite the fact that some of the conditions leading to that may come from Amazon themselves)
- It is harder to negotiate, as Amazon's official position is that "They do not work for us"
- It is easier to stop employment of sub-contractors.
The video already mentions this, but the idea of sub-contracting is that you are responsible for your own hours, routes, etc. This is clearly not the case for these workers.