Ideally, a mildly sick person should be able to go to a quarantine hotel of some kind and not infect people at home.
But if that person stays home, at least the infection spreads only to the people there, and not all over.
Business as usual would not result in fewer infections. New York already tried that.
By the time a person is even mildly sick it’s very likely the people at home with him are already infected themselves and just incubating.