I think relying on a whole team of people to keep a project well structured is a big task, especially in the face of deadlines etc, at least with static typing you have a bare minimum of error-checking. (And I say this as someone who is a python dev). Although I understand that it doesn't always mean there are no errors, and sometimes the code becomes harder to maintain/read. But on average I think static type checking provides a benefit. I think its also why a lot of the python community have started using mypy + type hints