Also there's some permanently running service. What's the point, to save 30 milliseconds out of the time to set up a VM which is certainly measured in tens of seconds?
(This is coming from someone who keeps colima running all the time on my Mac)
You're right that Docker on macOS runs inside a lightweight Linux VM (via Docker Desktop or Colima). We’re not using that VM to run the macOS guests - those run directly on the host via Apple’s Vz — but we do use Docker as a packaging and management layer (e.g. bundling noVNC, CLI tools, and configs).
So is it strictly necessary? Not really. But for teams already using Docker in CI/CD or automated workflows, it's often a tradeoff they're already making - and it means one less new tool/interface to adopt.
That said, we’re also looking into potentially using nested virtualization within the Docker daemon (which relies on Apple Vz under the hood) on M3+ chips, so as to remove the background service on the host entirely
Docker VMM, the latest virtualization option for Apple Silicon Macs, requires a minimum of 4GB of memory to be allocated to the Docker Linux VM.
Or so says an "AI", I'm not installing Docker on this laptop to check, I have limited RAM :)