We have this problem in the UK these days, in defence of these delivery men/women I have spoken to a few who are in the main Eastern Europeans, and they often have to provide there own van and all the running costs as well, and only receive a very small amount for delivering each package. They work 12 or more hours a day 7 days a week to make a living wage.
Amazon I believe are one of the worst offenders of exploitation, I often arrange the Amazon pick-up service where your package is delivered to a local corner shop etc. Speaking to the shop owner recently, they only pay him 20 cents per item, the transaction sometimes takes several minutes to complete, and creates a queue in the shop, its not really worth it.
Its another side effect of excessive capitalism in my opinion, we used to have a very efficient Royal Mail delivery service which returned undelivered items to a local office or leave it with a neighbour. This has been largely destroyed by multi-national companies creating delivery networks exploiting workers by paying very low wages.
I am not saying theft and scams don't go on, but a lot of the deteriorating quality in our delivery services, is I feel caused by we the public opting for low cost or free delivery services, which of course the system will create for us.