Docker-in-Docker not recommended for CI

I wanted to point out this blog post by the author of the original docker-in-docker implementation: Using Docker-in-Docker for your CI or testing environment? Think twice.

In summary, it says to not use dind for CI scenarios, when your only goal is to docker build or docker run something as part of your CI build.

Instead it suggests to simply bind-mount /var/run/docker.sock into the container, and run only the docker client (not daemon) inside the container.

This seems like a much simpler solution, and indeed the blog post corroborates that sentiment. What made GitLab decide to ignore this advice and still suggest dnd?

cc @ayufan