Windows container runtime is free as well, simply install the docker runtime from chocolatey or winget along with the Windows Containers and Hyper-V windows features. This is what we do on some build machines for CI.
Theres no reason to use desktop other than “ease of use”
Youre talking about Linux containers on Windows, I think commenter above was referring to windows containers on Windows, which is its own special hell for lucky folks like me.
Otherwise I totally agree. Ive done both setups without docker desktop.