While reading my 'news' feed on Facebook, I cam across the picture below for about the millionth time. I decided to respond.
1. It's possible to write lists in such a way that it's not necessary.
|Or you could say: We invited Washington, Lincoln and the rhinoceri.|
2. Sentences are understandable without it due to the fact that readers are accustomed to reading without it, thereby making making the rule unnecessary.
3. I do not use the Oxford comma in my writing. In 1 million published words, I haven't received a single comment saying something along the lines of, "I can only give this book 1 star due to the fact that there was no Oxford comma, leading me to unresolvable confusion."
All that said, everyone should write in the manner that works for them. The key is to understand the rules and make the writing understandable to as many people as possible.
And I will concede that it may be better to use the Oxford Comma than not.
All my best,
John H. Carroll