You must be talking about Horn & Hardart:
http://en.wikipedia.org/wiki/Horn_&_Hardart
They even had reasonable Thanksgiving hot meals on Thanksgiving for those that weren't dining with friends or family, or perhaps were working that day.
The workers at the NYC Horn & Hardart all seemed like they worked there a long time. It was a place to sit and eat, and watch the world pass by if one took a seat by the outer glass facades.
It was open 24/7 and was known for its hot serving line, and the little windows with cake, sandwiches, or whatever. Also the coffee server was interesting too.
I think it reflected a time in NYC that harkens back to the black and white movies of the 1940's. It wasn't obviously a "good time" for everyone; however, those who frequented the Horn & Hardarts sensed, I believe, they were experiencing something that would not last forever.
There was another 24/7 cafeteria in Manhattan at that time. The Bellmore on 28th Street and Park Avenue South, where taxi drivers ate, was the cafeteria that Robert DeNiro frequented in his role in the movie Taxi Driver.
Anyway, compare the calm demeanor of patrons in the Horn & Hardarts, of that era, with the sometimes frenetic activity in a fast food restaurant of today.