> It all boils down to making the employees working as hard as possible

This has not been my experience. The way I've looked at it as, these are more explicit ground rules for how decisions are made. At most other places I've worked, the mechanisms for making decisions was often quite arbitrary, and boiling down to whatever the most senior person in the room wants. When the Leadership Principles are done well, you'll see there are checks and balances built in. For example: yes, we have "customer obsession," and we try to work hard for customers, but if my boss told me to work unreasonable hours, he would fail in the "Earn Trust" area, and he would be in danger of losing his team.

I've found my work-life balance at Amazon to be pretty reasonable, and much better than pretty much any where else I've worked.