Currently, mount keybinds are very unintuive since they require action bar slots. Meanwhile, Extra Action Buttons and Zone Abilities have a dedicated, account-wide keybind that works across all characters and doesn’t get messed up with addons.
With so many different mounts needed these days—ground, flying, underwater, skyriding, D.R.I.F.T.—it’d be a lot more intuitive if mounts worked like Extra Action Buttons, where you would simply select the mount to be used for each type in a simple interface.