the sense in which one way is "wrong" is the same sense in which the oxford comma is argued: nobody is saying that civilization will collapse either way, but one way is tighter in terms of eliminating more common forms of ambiguity. And when saying 150 is one hundred and fifty, the "and" adds nothing in terms of information or comprehension; to that very same person, "one hundred fifty" is just as comprensible.

and fwiw, I don't think it's a regional difference, I think it's a difference between certain traditions within the banking and accountancy areas, vs outside.