I've been living in NYC for a while and whenever I sit at the top of stairs (in front of a building not in front of someone's house obviously), when I even stand for more than 30 seconds against an AMC wall or when I sit on a ground at a Barnes and Nobles (which I have done without any problems throughout the country) some security person asks me to leave. (BTW I dress like a student aka jeans and sweater and I am always very presentable just in case you were wondering)?
Added (1). *AMC theater
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Why can't people sit down outside in New York?