Why doesn't Docker map files to host?

Question

Windows

I'm experimenting with docker on windows. I follow the instruction https://docs.docker.com/compose/django/ . The "Create a Django project" step succeeds except for the third point. New files are created in the container, just like in a dock. But new files do not appear in the folder on the host machine. What is the problem?
Windows 10 Home, docker 18.03.0.