I think that I never saw somebody using Docker Desktop. I saw running containers with the command line everywhere, but I maybe I did not notice. No licenses for the command line tools, right?
On a Mac or Windows machine, you generally need something to get you a Linux environment on which to run the containers.
You can run your own VM via any number of tools, or you can use WSL now on Windows, etc etc. But Docker Desktop was one of the first push-button ways to say "I have a Mac and I want to run Docker containers and I don't want to have to moonlight as a VM gardener to do it.
The command-line tools on a Mac usually come from Docker Desktop. The homebrew version of docker is bare-bones and requires the virtualbox-based docker-machine package, whereas Desktop is using Apple's Virtualization Framework. Nobody runs the homebrew version as far as I can tell.
On Windows, you can use the docker that's built in to the default WSL2 image (ubuntu), and Docker Desktop will use it if available, otherwise it uses its own backend (probably also Hyper-V based).
I use Orbstack myself, but that's also a paid product.
