They cannot without involving way more material. The best isolation is the mass of the floor. Try moving around the second floor of a wooden building and check

They cannot without involving way more material. The best isolation is the mass of the floor. Try moving around the second floor of a wooden building and check if the glasses in some cupboard start to clash. If they do it is because the floor bends under your weight. The only countermeasure is to increase the mass of the floor and while a wooden wall (if planned for it) could certainly carry that weight it is difficult to obtain that mass from a wooden ceiling.