the most popular distribution still uses Snap
Ubuntu is the most popular? On server maybe, on desktop I doubt it.
Flatpak does not support CLI only applicatoins
It is not true. You can install Neovim as flatpak, for example.
Also some may like it more that Snap relies on AppArmor instead using the custom solution of Flatpak.
It only means, that on distros without AppArmor you get almost no sandboxing of snap applications.
The only advantage snap has is the ability to package drivers as snaps. Other than that there's simply no reason to choose proprietary-backed snap over flatpak.
EDIT: Typos.
No, optionally free is not enough.