When trying to start minikube with docker driver, as a root user I get:
$ minikube start --driver=docker
* minikube v1.16.0 on Ubuntu 18.04
* Using the docker driver based on user configuration
* The "docker" driver should not be used with root privileges.
* If you are running minikube within a VM, consider using --driver=none:
* https://minikube.sigs.k8s.io/docs/reference/drivers/none/
X Exiting due to DRV_AS_ROOT: The "docker" driver should not be used with root privileges.
What is the problem to use docker driver as a root user?