In reply to Richard Mellish, it has to be acknowledged that the folk process can work both ways, and that in some cases we have ended up with mere fragments, whether through poor editing of the story, mishearing or misunderstanding, or simple forgetfulness. However it does strike me that in many cases the printed sources are over-long, over-elaborate, and excessively flowery in their use of language. I imagine a longer song appeared better value for money when broadsides were being sold. Tastes change, but I wonder whether they were ever regularly sung in full or whether most singers chose to edit them down for performance, even when working from the printed version. The folk versions usually seem to reduce the story and simplify the language - whether that is degeneration or refinement seems to me entirely a matter of taste.