Some businesses close but during different periods of time, so while it's quieter it's important to note it's not shut down like a German city on a Sunday and there's always enough open at any given time to take care of people.

Also it's not like it being just quieter is the only thing going on - the city is also decorated for it, there are some celebratory activities (the parade), and there are different aspects of life like the supermarkets all play Chinese music for a few weeks.