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The comma after the second to last item in a list and before the conjunction is called, among other things, a "Times comma" (IIRC from the book "Eats, Shoots and Leaves") because it is required by the copy editors at the New York Times. Or was it the London Times? Anyway, it is optional in general usage, although it should be used or not used consistently within any writing. You are just as correct to write, "I like eggs, ham and orange juice," as you are to write, "I like eggs, ham, and orange juice."
I am an attorney, almost always leave that comma out and find that most other attorneys I deal with do the same (like in this sentence). If you have found that King regularly uses it, maybe his recent spell at jury duty changed him.
Until I became an attorney, I always used it. Now the law has changed me, apparently. Two exceptions that I still make for it are (i) if the list is composed of very long phrases, making it difficult to make sense of otherwise (although I am just as likely to use semi-colons to separate the items in that case), and (ii) where leaving it out would lead to confusion (this is rare; an example is "My wife, my daughter and I ate pancakes, eggs, and ham and cheese, respectively."--without the comma, it's hard to tell whether my daughter had eggs and ham and I had cheese, or my daughter had eggs and I had ham and cheese).
Now back to the regularly scheduled sports programming.
And please pardon any typos I might have made in this post!