I don't know the origins of the Dance Movie, but I suspect it's a modern phenomenon. I can't think of anything before Saturday Night Fever except musicals, and those were all films in which the fact that the characters were singing and dancing was never acknowledged. The Dance Movie inevitably features characters whose lives and loves are transformed through the act of dancing. John Travolta moves out of his class and neighborhood, Jennifer Grey publicly displays her attraction to Patrick Swayze, Jennifer Beals gives up her job as a welder (I wasn't really convinced by her welding anyway), etc. Usually, characters change culture and classes and the whole thing culminates in some big finale where the main character kind of screws up at first, and then shows her stuff, and everyone claps, and her enemies love her.
I think the world would be a better place if we regarded our lives as a dance movie. Dancing publicly would be the barometer by which we gage our success. It worked for African and Indian tribes...
Just for today, I can see my life as a dance movie.