NYC is one of the most challenging RF environments in the US for cell phones. Yes, there is ground-level outdoor coverage basically everywhere, but with many old buildings, indoor reception becomes a huge issue, and with a 114 year old subway system, people are constantly going in and out of reception, popping back up somewhere else, etc.
Further, due to the extreme densification of NYC, cell sites typically range from about 60' AGL (top of a 6 story building) to as low as 10' AGL (above the first story at street level), and their power is extremely low to cover just a few blocks where there are buildings that are 5-50 stories in many areas, compared to suburban CT where our typical site is 130-150' AGL and covers a 2-mile area that has, at most, 3- or 4-story buildings.
In fact, while in CT, most sites have a slight downtilt, in NYC, there are some that are tilted UP at close to a 45 degree angle to cover tall commercial buildings, and many tall residential buildings have unreliable cell service, as they are literally ABOVE the cell coverage. NYC is a VERY challenging RF environment for any provider.