would have no base whatever.

While affixes are grammatical (like prepositions), classical combining forms are lexical (like nouns, adjectives, and verbs): for example, bio- translates as a noun (life), -graphy as a verbal noun (writing). This is why some reference works also call them stems. They are also often loosely called roots because they are ancient and have a basic role in word formation, but functionally and often structurally they are distinct from roots