It is a massive organization that includes employees, contractors, and contractors hired by contractors. I've had Amazon deliveries dropped off by UPS, FedEx, USPS, white vans with the logo of local independent delivery services (contractors hired by contractors... that's Amazon Logistics), and random people in their own cars using an app on their phone (contractors... that's Amazon Flex).

What makes you sure they aren't contractors? Ask them the next time you get a delivery.

They may drive trucks with the Amazon logo; they may tell you they are delivering for Amazon; they may be driving around with an app made by Amazon that gives them step by step instructions of what to do. But they are not legally employed by Amazon. Not in the US or UK. I spent some time as a part of their software organization, and have been inside the delivery stations. As far as I know, there are no employees delivering packages.

You can speculate as to why Amazon would want things setup this way. I don't speak on the company's behalf.

I did ask them, the guy I talked to was an Amazon employee. I wasn't just assuming when I made the comment.