The last thing I need at the end of the day is to look out the train window and see a small penis waving in my face. It does not impress me how discreetly you can masturbate on a station platform and, really, I don't need the private show. Sorry, but girls like me don't like guys like you. And if you were waiting to get off on the "oh, the horror" reaction, sorry again, because unfortunately a lot of sick fucks have preceded you.
Keep the fantasy, buddy, because you are going to live a very lonely life.