Lots of code in the stdlib does not have type annotations. Though I think most popular modules in the std either are annotated or have stubs somewhere.
I don't see why they would introduce _new_ code without annotating it, when that's clearly the trend for 3rd party libraries. From a quick look, it doesn't seem like it would be difficult to type either.
Though, I agree that typing everything is good. Especially when combined with a good typechecker like pyright.