Podman out the gate has had the facility, which I think it used as a means to distinguish itself. This is great, because maybe that helped push Docker in the right direction.
https://github.com/AkihiroSuda/docker/commit/588a4e91fc8cb99... https://github.com/containers/podman/commit/19f5a504ffb14709...
Rootless Docker wasn't merged/released until Docker 19.03, though , but still it is already nearly 4 years old.
Podman is just an app. It’s like Vim or ffmpeg. Imagine if Vim ran as a root daemon at all times and you ran sudo to connect to it and edit text files in your home directory. That’s how silly the Docker architecture is.
One beautiful thing about Podman is it can fire up, pull the image from the container registry, start the container and then go away. Leaving you with only the containerized application running in rootless mode.
To do this with Docker, you fire up the entire Docker infrastructure, then launch the docker client, once the application is up and running, you still need to shut down the docker infrastructure.
Even if you run with podman socket activated server, the podman service will not be running until someone connects to the service, once the connection to the service goes away, the podman service shuts down no longer using system resources.
Both Docker and Podman support rootless mode (and rootful mode).