Amazon is a pushy company that does NOT understand what it takes to get a pkg from point A to point B. They demand extra services for less money, and make demands that no delivery company can accomplish on a daily basis. They expect every day to go flawlessly from a performance standpoint, have perfect weather, and every address is easy to find and a breeze to deliver to. Lemme tell ya, thats not how real life is. Bezos lives in a bubble.
When/if they get their "fleet" on the road, it'll be a bunch of minimum-wage paid people using unserviced equipment (or their own vehicles). It'll end up a complete nightmare for them, from financial and service/claims issues to consistency/reliability/reputation fallout. Meh...might last a year or two, then they'll be back, tail between their legs.