That repetition of the first verse is something you get in certain poetry too. I think the effect is much the same as with certain songs: it brings new meaning to the verse you heard first, because now you know the story that it was introducing, and understand the significance of what it told you. It can bring a certain irony (popular in late romantic poetry) and sense of knowingness or regret.

On a practical level, it makes it clear that you're winding up the song, and (Jim Carroll won't approve of this, but it's common in England now) allows your audience to join in because that first verse is more familiar to them now. I like this; it gives the audience a chance to express their endorsement, their participation in the sentiments or the story of the song.

Marje