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The comma originally was used as a pause or breath, to better emulate the flow of speech; as literature was still beholden to oral tradition.
If you drop the oxford comma, it adds flexibility to the prose, allowing commas to indicate cadence of speech.
It's ironic that the dash originally served the same purpose (as a rest notation), but now is also used to group like terms. The ellipsis is not suitable for this function, because it always implies an incomplete statement...
