Whether you do or don't is a matter of personal taste - my intervention was purely based on the statement that it was an old practice.
I don't see the need for it, particularly in narrative songs - it has to spoil the plot.
Joining in on the last verse wouldn't make the slightest difference anyway - if you've gone back to the beginning of the story you would have spoiled it for me anyway
I believe it to be a modern affectation, that's all.
Another affectation is the use of recitative, a straight lift from the music-hall and the Vaudeville stage.
As Marge says, in general, I detest joiners inners ; if I still lived in the U.K. I would attempt to organise an annual cull.
Jim Carroll