Why you gotta talk so loud?!

You may be having fun, but please keep your voices down.

This one, I don't think it would go over quite so well in the New York subway. You can just bet that a bunch of feminists would be all like, Why'd you have to use women to illustrate people talking too much on the train?!
Because you know how women are. Noisy!
Really, though, the groups of people I've personally witnessed being noisy on the train are, in order, first, groups of Americans, especially beefy guys, but mixed-sex clusters of skinny 20-somethings are super racket-prone, too, especially on an afternoon train toward, say, the beach; next, Japanese middle or high school kids in sports uniforms, maybe on a post-game high and usually with a pair of den-mother chaperones ignoring their rowdiness; next, groups of three or four swaying Japanese salarymen, collars open, redfaced and repetitive on the way home at night; and last, by a lot, pairs of young women who are all like, you know, and-then-he-was-like, and so on. 
So maybe they didn't choose the actual noisiest, but the least likely to complain about being portrayed as such. Maybe the first draft was a bunch of US military guys tossing gum wrappers and plastic bottles at each other across the aisle, and then someone thought better of it.