That is no longer the case in most urban areas where food trucks proliferate. These aren't the sandwich and coffee offerings at construction sites, but a variety of ethic and gourmet offerings. Lunchtime is def big business, but these guys do a good evening and nighttime business, as well. The dessert trucks do particularly well in the late afternoons and evenings, and the late night munchers need something when they get out of the bar or club to help soak up that alcohol. On biz travel, I've picked up a gyro or something else from the trucks on occassion in NY, if i left the office very late and wasn't in the mood for a sit down meal somewhere but needed to eat.