Culture, recreational activities, demographics, etc. vary quite a bit in other "twin city" type situations as well. Dallas and Fort Worth are about as culturally different as you can get at that distance, and of course people don't live downtown in one and work in the other - people are making a very specific choice with very specific tradeoffs when it comes to living in a downtown area in general, and those don't make sense if you're not explicitly spending most of your time in that area. Income is about the only thing that doesn't hold true in the Texas and Minnesota examples listed elsewhere in the comments, and DC has some conditions fairly specific to it that cause that.

I don't have a link but I remember reading an article/Blog post linked here on hn where a software developer was in San Francisco one evening, saw the cops arresting someone, went to say something, got arrested himself and they held him over a long weekend or something in terrible conditions, and the police officers said some terrible things like the person he arrested was overpaid and the officer had to live in Oakland or something.

I've never been to SF/Oakland but this is one of the first thing I think of when the place is mentioned. How is the employee to blame for structural/ societal issues. What kind of idiot dumps their frustration on just some passer by?