Some great discussion here now, too much to respond to in one go. And most of it well-informed anyway.

Tzu, if you turned up a broadside ballad without a strong rhythm then you were extremely unlucky. The vast majority at least have a reasonable rhythm and form, and those that don't soon acquire it if the song content is usable. I am guessing here and basing this on my own songwriting but a useful ploy in writing this material is to have a tune in mind while you're writing, regardless of whether that tune is eventually used.