Caps or quotas are a better way to achieve this IMO. Random shutdowns do not make it sound as if DO is ready for production.

It's not just the volume of usage that can indicates fraud, but the pattern. In addition, relying on quotas creates a system that is easily games by perpetrators of fraud.

Caps or quotas are not sufficient to deal with this problem.

If a cloud service is supposed to be ready for production, then customers should be safe to assume that they will not simply be shut down, especially not without warning. Otherwise, the provider must make clear that the service is only for hobby use and not for commercial use.

Every single major cloud service provider will shut you down without notice if they detect obvious fraud.

What kind of fraud do you have in mind and do you know of a case in which, for example, Azure switched off an enterprise customer due to unusual usage patterns?

Caps and quotas limit the size of the chargeback.