PaulG at 2015-01-16 17:02:09:
Set in the depths of the Great Depression, the movie can be viewed as an allegorical critique of capitalism, its exploitation of labor (the dance contest), speeding up the production line (dance sprints), winner-takes-all reward system (the last couple standing wins the prize money), the cynical, callous manipulation of people's dreams, and mystification ("It's only entertainment, folks.") What made the movie even harder for me to watch was the knowledge that grueling dance marathons were a popular fad in the 20's and 30's.
The only explanation I can think of for how such a grim movie with a downer ending got made was that the 4 credited producers (Irwin Winkler, Robert Chartoff, Johnny Green, Theodore Sills) had personal knowledge of the Great Depression. They didn't forget how hard times were, and didn't want the world to forget either.