I always just assumed it was a gruel rather than soup that we think of today. Some sort of slushy paste with rare bits of bread or meat sprinkled in.
Soup's not really that filling, but I'd be pretty disheartened if I had to eat gruel every day. If I had a 14 hour shift seven days a week only to come home and find the only enjoyable part of my day, eating my dinner an hour before I have to sleep for tomorrow, I think I'd start complaining. Then again, when the alternative is dying, I don't really think I have any right to complain since it's either this or death by starvation.
I'm kind of surprised there's not a wider range of management options for discontent and general laws. For example, Hearty Meals not becoming part of the base game in Endless, or not getting two shifts or relaxed shifts as options. It'd be kind of interest to have a city council that forced some laws on you from time to time so you don't just always pick the best.