Because the auto setting is only relevant to the form functionality itself, so you have to be in the form to realize its functionality. If you are using the "submit to email" submit function, then it just simply emails a snapshot of what it thinks it sees and does not follow the formatting of the form settings itself very well. I would suggest making an email-firendly view that users don't see but that has fields set to auto-height and auto-width to accommodate larger sets of text. You can't realy make it dynamic in this case, which is unfortunate.