Why it is vitally necessary to prevent the extinction of the final serial comma

From Bruce Baugh via Patrick Nielson Hayden via Brad DeLong, here is a photo caption from a story about Merle Haggard:

The documentary was filmed over three years. Among those interviewed were his two ex-wives, Kris Kristofferson and Robert Duvall.

Were Merle & Kris & Robert ever actually married? Somehow, I doubt it. My guess is that the passage in question should have read:

Among those interviewed were his two ex-wives, Kris Kristofferson, and Robert Duvall.

Can anyone think of a good reason to leave out that last comma in a series? I can't. In fact, the practice has always irritated me. It belongs in the historical dustbin of English usage.

Yours for logical punctuation,
Jeff Weintraub