I think it’s a quirky thing

That’s funny, because I didn’t even notice it.

In my own writing, I usually try to be very consistent, unless I am intentionally trying to make a joke or keep things light. And in those cases, I am very deliberate in my use of mixing the styles.

But in reading someone else do this, I didn’t even notice.

I suspect to emphasize enumeration so readers don’t incorrectly parse the sentence. But the text would be even clearer had these speech patterns been omitted altogether.