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"And I got to wondering about the 'folk process' trimming many songs of extra verses, versus a general lack of interest in keeping the richness of the originals." Forgive me if I've misunderstood your statement here, but the 2 items 'versus', aren't they the same?

The general idea of the folk process is that the trimming of extraneous material is more often than not an improvement in the mouths/ears of the folk who preserved/mediated them. Otherwise we'd all be dashing back to the broadsides and sheet music for the earliest versions.