My experience with shipping companies (no matter which one, and in 4 different countries) is that they generally don't manage to deliver a large fraction of packages. The failure rate must be above 20%, which would be unacceptable for most other kinds of systems.
Every now and then someone convinces me to try Amazon - my most recent experiment with it involved 3 orders, of which they managed to deliver 1. This is to an address in Central London.
I guess you might have a different experience with shipping services in the very grid-like, regular, easily adressable American suburbs - but IME in Europe the most reliable way to get some goods is still to buy them in a physical shop.