That scenario implies that someone has made a mistake. They forgot to turn off a service or turned on a service by accident. How does AWS know that the billing cutoff wasn't the accident? Maybe I accidently set a $20 cutoff during building my MVP instead of $200, but now that I have a paying customer I'm going to hit $100/month. AWS could disable my very first customer because I forgot to fix my billing setting.

Doing nothing is generally better from a legal liability point of view. The customer should be liable for turning services on and off.