Your position is based on an absurdity JC. To say the people wrote them is as nonsensical as saying nobody wrote them.
At some point they required a founding author, even if that writer's efforts have become debased (dressed up as popularised) by repetition. The stimulus for their adoption relies on the permeability and attractiveness of the original product.

To use a pop example Annie's Song is still the work of John Denver even when an unknown Sheffield Utd songsmith changed the words. The sensibility that inspired it is still recognisable and intact. Even when a bit naff, as in this case.