And pydantic isn't really about type checking either. In fact it says that in the first few lines of the it's docs https://pydantic-docs.helpmanual.io/usage/models/ :

> pydantic is primarily a parsing library, not a validation library. Validation is a means to an end: building a model which conforms to the types and constraints provided.

Anyone whose used Typescript or even strong typed languages knew what to expect from Python + mypy. No surprises there. But pydantic's use of type hinting to create a remarkably dense serialisation library, and then fastapi's leveraging that to create REST interfaces along with automagic documentation generation - well that wasn't when I was thinking would happen when I saw the type hinting proposal.