I get what you’re trying to tell me but having a single day where everyone is out doing stuff sounds like a recipe for an overcrowded, miserable experience. I don’t WANT to go to the café when all the tables are already taken and there’s a longer wait to get a drink, or go to the museum when all the planetarium shows are already sold out and there are masses of people standing in front of all the exhibits.
While not as universal as wherever you lived, the tendency here in the USA is still for the majority of people to have weekends off (and especially Sundays), and I often try to avoid going to restaurants or attractions as a direct result if I have the option to do it on an “off day” instead. Maybe you’re just more of a people person than I am. I do imagine it makes things much easier for activities like personal get-togethers, parties or board game nights, though.
EDIT: And of course, not forgetting that in the USA we kind of don’t live in a society so much anymore… 
