Why so averse to direct Python?
Slightly related question: why do people love Python so much? Or, any dynamically typed language? There's almost nothing that has frustrated me more in a professional setting than trying to figure out what some dynamically typed code is doing and ensuring I don't break anything by making changes.
These aren't just some third-party tools bolted on. The type annotation syntax is built into the language[5] and standard library[6][7].
I personally find static typing to be more trouble than it's worth most of the time. Industry typing metalanguages are not expressive enough to deal with even fairly basic real-world programs and force you to write bad code to work around the type checker's stupidity. And, of course, you still have to write tests. Maybe someday they'll catch up to Idris. Python's static typing is no better, but at least it allows you to turn it off when it's not worth it.
[1]: https://github.com/microsoft/pyright
[2]: https://github.com/python/mypy
[3]: https://github.com/google/pytype
[4]: https://github.com/facebook/pyre-check
[5]: https://peps.python.org/pep-3107/
[6]: https://peps.python.org/pep-0484/
[7]: https://docs.python.org/3/library/typing.html#module-typing