These phrases are heavily influenced by French, even if they don't follow all of the exact same rules. "Not pluralizing adjectives" is a more ingrained rule of English than "adjectives come before nouns," so with these phrases, the latter rule is set aside in favor of "Frenchness" while the former rule remains in place.

The messiness of English is directly because of all the different influences from other peoples and their languages over the centuries; it's not "just what English does" without reason.