Question: According to the Wikipedia page for the [Oxford Comma](http://en.wikipedia.org/wiki/Serial_comma#Arguments_for_and_against), "Use of the comma is consistent with conventional practice" and "Use of the comma is inconsistent with conventional practice." Did the Oxford Comma come before its omission, or was the Oxford Comma traditionally omitted?

It makes logical sense that every item in a list would be separated in the same way: by a comma. If the Oxford Comma is conventionally correct, when and why did people begin to omit it?

Answer: 
If find the Oxford comma to give fair representation to how people speak. When listing items in speech, equal pause is given between each item. For me, the Oxford comma emphasizes that there is, indeed, a pause before the 'and' preceding the last item of the list.

I think the Oxford comma also indicates the direction of the sentence -- it makes it clear that you are reading from a list. Often I find myself rereading sentences that don't make use of the Oxford comma because, on the first pass, I have misunderstood what they are saying.

But, as your question points out, many do not use the Oxford comma (e.g., The New York Times).
According to Willam J. Strunk in *The Elements of Style*, Rule 2 states that a comma should be used after each term except the last in lists of three or more items. There is an exception which is in names of businesses, the correct example given is: Brown, Shipley and Company (as opposed to Brown, Shipley, and Company).

See the link for the full online text:

<https://faculty.washington.edu/heagerty/Courses/b572/public/StrunkWhite.pdf>