As stated at https://www.docker.com/docker-windows
"An integrated, easy-to-deploy development environment for building, debugging and testing Docker apps on a Windows PC. Docker for Windows is a native Windows app deeply integrated with Hyper-V virtualization, networking and file system, making it the fastest and most reliable Docker environment for Windows."
It requires Hyper-V (More info here)
- ... and Hyper-V requires this