When you look at that map, the majority of manhattan doesn't have fios available, let alone the other boroughs.

What? http://i.imgur.com/r6ZJny0.png Looking at that map, it's not clear at all that Manhattan doesn't have coverage. And this is only what's within a two mile radius of the center.

It only looks like a lot when you're not zoomed in. The density here is very, very, very high. The vast majority of buildings aren't covered.

FiOS in NY is expanding very slowly (not just in Manhattan but in all 5 boroughs). Staten Island got more coverage than most, because it's less urban. Constructing in the middle of the city is always way more expensive, and Verizon is not rushing to do it.