Probably because most people define 'urban' and 'suburban' in relative terms, and a neighborhood that might well be 'suburban' by NYC terms is 'urban' by the Seattle definition. Or a 3000sqft. house on an acre lot in Orlando can be 'downtown'.
NYC in the example is very urban, but Staten Island is about 3x as dense as the (very suburban) suburb where I live -- and it gets very rural out here very quick (we're mostly converted farmland at this point). Staten Island seems fairly suburban to me, lots of single-story family homes with yards. It's almost the definition of a suburb except it happens to be administratively within NYC boundaries.
Manhattan is about 30x as dense as where I live and there's nowhere within 15-20 miles of where I live that even looks as urban as Manhattan. Mile after mile you get multi-story highrises or tiny squashed multi-story town homes that are mostly stairs. Even if you ignore the biggest skyscrapers, there's very few other places quite like it.
How "urban" a city is and what the limits of a "city" are. Both of these are fungible by the community, as they should be. Urban living where I grew up would probably still include a backyard, in SF it probably includes a garage, in NYC it includes neither. The city of SF is pretty strictly defined, but the city of San Jose certainly has more fungible boundaries as well (santa clara vs milpitas vs san jose).
I live in a rather nice area that has sidewalks only where new homes have been developed. There are huge stretches of roadway (some at 40mph) where riding on a bike equates to having a death wish. (Yeah I know bikes are supposed to be on the road, but at speeds above 20mph or so that is also complete bull!)
We have a mileage here where the city does all the sidewalk work. It's pretty awesome, no more tripping on cracks. I think it's like $15 a year for my $200,000 home.
http://m.metro-magazine.com/news/292617/poll-americans-favor...