As you weave among the obstacles on the sidewalks of Manhattan, it's easy to get distracted from your thoughts and pay attention to the people you're encountering. It's okay to do that if you're at a stop, but if you're in motion, if your eyes engage with another that signals that you would like to negotiate. Not good. A sign of weakness. Whether the oncoming traffic is aware or not, he or she will take advantage of this weakness and charge right into your path, all the while not making eye contact. There is no appeal.  

All you can do is shift out of their path, but even this won't avoid a collision because your adversary will unconsciously shift closer to you. Your weakness is attractive. Your space is up for grabs. At this point you have no choice but to collide, and in the etiquette of NY street walking you're responsible.  

That's why the people who check their smartphones for text messages or emails while walking so totally command the sidewalks. They are heat-seeking missiles, and it's your heat they seek. 

I don't think this is just New York, it's a feature of the human species. We seek companionship.  

For a while in 2005 I lived on the beach in northeast Florida outside St Augustine. The beach is so long and relatively empty, they let you drive on the beach to find the perfect spot to bathe, and if you're willing to drive a bit you can be alone. So I would drive to a secluded spot, park my car and go out into the surf. When I came back, more often than not, there was a car parked right next to mine. They could have parked anywhere in a mile in either direction and had it all to themselves.