These are also all hospitals in higher-income areas that can be considered part of the larger NYC metro region, as it is home to many of the bridge-and-tunnel commuting workers. I would not be surprised if this demographic has a statistically significant deviation from the national norm when it comes to seeking certain medical services and attitudes on desired level of medical intervention during childbirth.
Furthermore, very-high-income areas (North NJ must have the highest furriers-per-capita in the US) tend to have a far higher median maternal age, which raises the likelihood of c-section.
This is purely a hypothesis, however.