The oxford comma, also known as the serial comma, is one of those pieces of grammar that no one is ever sure if they should use or not. For several years the oxford comma was the norm, but lately it has fallen to disuse and even gets edited out of writing.
A main reason that the oxford comma is getting used less and less is because it’s just an extra, unnecessary character. In a tweet-able world where every character is sacred, it makes sense for people to drop the extras. This is also the logic behind only having one space after a period, instead of two.
I am a big supporter of the oxford comma (and two spaces after a period), but that’s just me. According to Oxford Dictionaries, the oxford comma is a comma used before the word “and” at the end of a list.
Check out this humorous example: