Must be a variation between IMAP and Exchange connections. Mine do not appear at all. But still, isn't that better seeing the the Mail app will open to the inbox anyway? You therefore won't see the extra folders unless you select the entire mailbox.
My Outlook folder list using IMAP is exactly what appears on my iPad and iPhone. In Outlook as you know you can collapse the sub folders and I have it in an order that I really don't wish to change so it is like dealing with a Catch 22 situation.