I think people are forgetting how hard this can be... an EC2 server is easy enough to turn off but AWS has dozens of services charged at very fine-grained levels. How exactly are they supposed to stop spend?

The only way would be to completely reset the entire account, otherwise you'd still be accruing charges just for data at rest or incoming requests or anything else passive.

A complete account reset doesn't seem like a feature that's very useful or something they'd want to implement because it would likely cause more trouble then help fix.