Dick,
The contentious issue is the ORIGINS of the songs. The fact that almost 90% (probably more) of them first appeared in and are extant in cheap print is indisputable.

The 'romantics' contend that they were mostly taken from oral tradition before they appeared in cheap print, the 'realists' contend that they originated under some form of commercial conditions, be it theatrical or cheap print poets in the towns. These 2 terms are Steve Roud's not mine but I see where he is coming from.