Draperies and furniture often improve the acoustic of a room. Why?

According to Sabine, acoustic of a room depends upon its time of reverberation which can be adjusted by placing such things in the room which may absorb the sound falling on them. As drapeness and furniture in the room absorb the sound produced in the room, they help to control the time of reverberation of the room. Therefore, the presence of draperies and furniture often improve the acoustics of the room.