Commas congregate around the edges of rules. Some exist within the realm of necessity, but most commas waltz through lawless zones, following nothing more than a song in the author’s mind, required only, by their presence or absence, not to confuse or trip up readers.
Actually the Oxford comma is not a rule.
My own preference is to use Oxford commas—mainly for consistency, because so often they are needed for clarity.
But different writers fold language into different patterns. Some prefer to avoid commas wherever possible. Some sprinkle commas onto the page like pepper onto a potato. And that’s okay, as long as the text flows for the readers, as long as the story lives in their minds. If we all wrote the same way, books would get pretty dull.
(As your editor, I work to defend your style—or, if it’s your preference, bring it into alignment with the Chicago Manual of Style.)