If the NY subway is anything like London, people will be less than 6 inches apart at rush hour. I imagine that will have played a big part in the spread in both of those cities.
EDIT: typo
Widespread mask usage doesn't happen in NYC, same as the rest of the U.S. It's very recent this is practiced in the U.S., whether voluntarily or by order of a handful of local governments. And in my local area where it's not mandatory I only see about 3 in 4 using masks.
NYC has a culture of yelling.