Comment by jjgreen

You know, I really don't know: it always looks strange and wrong to me. I can live with American fondness for the "Oxford comma" (enumerating "one, two, and three"), but that has some justification in terms of clarity (if the final item has an "and" in itself, like "ready salted, paprika, cheese and onion" crisps/chips). So "just because" seems most likely :-)