Actually, it's a hub, served with innumerable destinations from New York Newark Liberty Airport.

I really don't understand this fascination with pretending that Newark is somehow a less worthy airport for New Yorkers than JFK or LGA. I've been to all three of them, and none of them seem likely to win any awards.

If JFK is more convenient for you, great; use it. But United advertises in NYC because for many travelers to/from the city, all three airports are equally inconvenient. LGA even has the ridiculous perimeter rule in place; in fact, I believe United is the only carrier there with daily service beyond the perimeter.