It's is one of the necessary myths of the tradition that it is under attack. As others have intimated, there's little evidence unless you equivalence horse-drawn transport as under assault from motor cars, or steam from electrification. I doubt Lumiere's motive in projecting moving pictures was to marginalise live performance any more than Vaudeville sought to institutionalise and codify entertainment practices; they just sorta evolved that way.

Folk is not dynamic in that sense. It chooses an historical framework and seeks to valorise it, or suggest emblematic national status. It can't evolve because it suggests the conditions that gave rise to 'folk' no longer pertain but insists that other cultural processes endanger it's wider dissemination. It seems like cake and eat it to me - stop the world I want to get off. It doesn't stop me liking the noise or admiring the work of those who take their tradition seriously but the attack stuff seems like a wagon circle when there ain't no Indians/Native Americans.