"Antiquarian poets": gave me images of greybeards composing "old" ballads between extolling to customers the virtues of Chippendale tea-chests and ormolu clocks.

Can you briefly explain why most Child ballads are presumed by the informed not to have existed prior to the broadside age, and instead to have been artifacts of the broadside songwriting industry (if I understand the point of contention here)? What traces of them should exist that apparently don't, in contrast to other ballads from earlier times that we do know of?