I have what I guess would be considered a rare recording of some sort of town hall evening with Kander and Ebb playing and singing their own songs and telling stories about them. It was recorded sometime before the original Chicago opened because they presented an early version of the song Roxie from their “upcoming project”. On that recording they say Money Makes the World Go Round was written because Fosse thought the audience would like to see Joel and Liza sing something together. Since they do not in the stage version. Assuming that is correct, there’s the reason! Of course when it was interpolated into the revival Sally was no longer a participant. I like the way they used to further the smuggling plot point.
That is fascinating stuff! Just to double check, I reviewed all the revival recordings of Cabaret, and none have the Emcee and Sally do "Money, Money" as a duet, as in the film. All the stage revivals have the Emcee performing the song alone.
