re: Why does every Bollywood movie have an unrelated dance and song number?

There's some controversy in Asia over the Bollywood trend to cast light-skinned actresses. It's gotten to the point where they're casting actresses from South America and other places to portray Asian woman.

And, FWIW, the AMC theaters in Baton Rouge often have a Bollywood film showing. Very few people in the audience and they're pretty entertaining.