NYC is definitely very different from just about all other cities in my experience. I visited many large cities growing up, and now live near many, so I thankfully learned at a young age to adapt to wherever I'm visiting. However, some people have never left their small town, or consider Omaha, Nebraska to be a large city.
There is a certain way to act and walk in NYC that will keep scammers away from you and prevent you from being run over by cars, or other pedestrians. Anyone who doesn't know this generally has a bad time and thinks New Yorkers are assholes, but they're very nice in my experience. They become rude when you inconvenience or are inconsiderate of others.
Two examples from the last time I was working there:
A couple with thick southern accents being harassed by some dude with CDs because they didn't know how to say fuck off and just push through him. After about 20 seconds of them being stopped someone with a thick as fuck Brooklyn accent tells the guy off for them, and walks away without acknowledging them while bitching about tourists.
Someone stopping in the middle of the sidewalk at 12:30 pm in Manhattan to look up at some tall building before getting ping-ponged between 3 people shoving past them until they ended up on the edge of the sidewalk where they belonged.
In my defense, not seeing any buildings bigger than a barn until you're about ten, and not many more until 16 then going to NYC on a girl scout trip did almost cause a panic attack.