Much of what we are discussing here seems to rest on the FACT that the great bulk of commercial songs should be considered as 'unsingable', 'doggerel', 'too long' etc. Having spent most of my life 'grubbing' through the dross to find the 'jewels' I can absolutely verify this.

However, what you MUST take into account is the obvious point that the bulk of this material was indeed discarded and not retained in oral tradition. You are comparing millions of commercial products with a few thousand that actually went into oral tradition, for a variety of reasons.

Brian makes an excellent point with 'The Wild Rover' and there are plenty of other similar examples.