in business-communication top posting and TOFU is normally
because with TOFU you need only the last mail of a conversation
and with the top-posting you need not to scroll and see the whole
answer in the preview after select a message
so this is all a point of view
But business email is not normally archived for later use. It is
essentially one time communications with a few exceptions. And this
difference is essential between a mailing list and simple email
exchanges.
Just my 2 cents worth, and that ain't much these days