If you ask most people why they airbnb over hotels they say its because I can take my family or group of friends to an airbnb, where as in a hotel we'd need to get 4-5 rooms.
In most other cities you can trivially find 5 bedroom places that fit that bill. In New York I'm not sure you can find alot of 5 or 6 bedroom places, especially in Manhattan.
So airbnb's main draw for most people just isn't available in New York in a way that it would be in most other large cities.
Which means you'd expect alot less people to use airbnb over a hotel in New York.