It'd be interesting to see how much business is B2B and repeated addresses for UPS/Fedex vs Amazon.
Amazon is likely to be distinct. High amount of one off consumers. Varying routes every day. Customers being away during delivery. Exactly what ruins a delivery company.
Also, "one off consumers. Varying routes every day." Well, delivery company employees will have precisely fewer of those because their job is to deliver things, seems like the reason not to trust Amazon drivers over Fedex.
It's not your dream job. My last cab driver immigrated 16 years ago and has been driving 5pm-5am shift for the last 7 years. Full time delivery is a dream in comparison. I don't think he could send his kids to college on Uber.
It's healthy compared to desk work, doesn't require any extensive training, and relatively low stress.
Be cautious when predicting the behavior of others.
Did you ever have to deliver to someone who is away? to an address that doesn't exist? to an address that exists but is located at the wrong place? what when it's inaccessible or has no bell?
That's what you get to deal with every single day, you never know where you gonna be or what's gonna go wrong the next hour. Meanwhile, your delivery time is accounted and customers can complain back about you for anything.
Maybe not now, but it used to be. You say that the job and work conditions can't be improved, but the fact that they were better before proves that your statement is false.
I'll reckon, any job was better 50 years ago when rent was a fraction of a salary and you could provide for a family on a single income.
You can't significantly improve the job and the work conditions, it is what it is. You can't pay more, that'd impact costs too significantly.
The consequence is high turnover and you can't fix the root cause. Lucky you, there is an endless supply of fresh blood that can and are willing to do the job so it's a viable business model.