Bringing it back to folk, it shows there are only a fistful of warhorses making up the classical repertoire, and probably fewer in total than in the folk repertoire - it probably evens up when themes are taken into account, though, as a symphony will have a fistful of "tunes" which get worked out in the rest of the piece, much like we'd do variations on a set.
Thankfully nobody expects us to don monkey-suits, though.