keeping your credentials safe instead of relying on amazon sounds a lot easier to me
your argument is like saying a daily withdrawal limit (like $500) you can lift at any time isn't sane, because "keep your card and PIN safe" sounds a lot easier. Well, yes, but the point is your card/pin can (and does) get stolen, and so do Amazon credentials.
I just don't understand why they don't add that extra layer.
(Well, I can understand. If 98% of the clients with stolen access are huge companies that have no idea whether their charge should be $170 or $85,000 per month and are happy to pay either, then the policy might make sense to Amazon. But that doesn't seem likely, as they go out of their way to try to reach you and notify you that this might be happening. . .)