In my opinion, it's so easy to get into the habit of using an Oxford comma (and I've only ever seen benefits to using it and not drawbacks) that I don't see why anyone wouldn't. :) It sends the message to other folks that it's a good idea, too. It's the same with putting a comma before the person you're addressing (in direct address). There's only upside, and never downside (unless you consider wasting a few neurons, a few pixels, and a negligible amount of time downside; what else are you gonna use those resources for?). :)

Sometimes there is a good reason to use the Oxford comma, especially if you need to separate the last two items on the list. Here's a good example, taken from a question that was asked a short while ago, with thanks to the OP and to Phil who corrected the sentence: "my mother's best home cooking — broiled fish, fried cabbage, and lobster." The corrector chose to add the comma after cabbage to indicate that these were three separate dishes. Without the comma, we would understand 'fried cabbage and lobster' to be a single dish. Another classic example is this: "I'd like to thank my parents, Arnold Schwarzenegger and Mother Teresa of Calcutta." versus "I'd like to thank my parents, Arnold Schwarzenegger, and Mother Teresa of Calcutta." Unlikely, but it's one you'd remember!

Actually, the last comma comma before the "and" in a list is called an "Oxford comma," and there have been PhDs written about whether or not it should or should not be used. The debate about whether or not to use the oxford comma is probably as old as the English language itself. Ultimately, it depends on your style. If you're following a standard style of writing, it might dictate whether or not you should use it, otherwise, it's up to your discretion. Here's an article listing some pros and cons to using or not using it: http://mentalfloss.com/article/33637/best-shots-fired-oxford-comma-wars

Personally I have never used a comma before and and I very rarely see it used by anyone else either.

See more examples... http://www.italki.com/entry/357859 https://www.italki.com/notebook/718609/entry/376810 (see the attached image)