In my eyes, the situation is simple: human beings are fallible. If there's a chance of your credentials leaking and being exploited that way, that will most certainly happen to someone sooner or later.
I recall a VPS that i had years ago being hijacked due to Docker socket being exposed publicly (when i set one up for testing and was just learning about Docker), which was mining crypto throughout the night before i noticed it.
Imagine what would happen if there had been some sort of auto scaling in place and i had used a managed Kubernetes solution (many of which didn't yet exist back then)...
Is it Amazon's problem? Not really, apart from the bad PR that charging private individuals exorbitant sums (for them) might cause, so sometimes these bills are waived after people mess up. For the corporation at the size of Amazon, that's probably not too much in the grand scheme of things, but it's also understandable why people might be appropriately upset about not being able to set hard spending limits, merely alerts (which aren't enabled by default).
That's just the reality that we live in for now, however one can also think about why a corporation that cares a lot about uptime might not necessarily want to implement functionality that'd let resources be easily cut off when spend limits are hit or something similar, since most businesses that utilize their services might just swallow the occasional expensive bill like that anyways.