The whole concept that there are "core AWS services" living in one single zone sounds like anti-thesis to everything AWS should be about. What's the use of havi

The whole concept that there are "core AWS services" living in one single zone sounds like anti-thesis to everything AWS should be about. What's the use of having all this nice distributed setup - and paying for it! - if a single failure in a single zone takes everything down anyway? I mean sure, maybe they built it on a shoe-string budget years ago - but since then, they had years and billions, and still didn't bother to fix it?