Walls are made only for privacy. Therefore openings can be as large as is required for design. Traditional box-like rooms were destroyed. With R.C.C. structures, walls can be straight or curved. Spaces started flowing from one room to another, from interior to exterior.
Light quality is improved.
Dynamic and adventurous forms are experimented with. Today, large openings, free plans are so common that we take them for granted. Since antiquity, rules of proportion are followed to bring unity, harmony and rhythm in architecture. Suppose a normal room of 16 feet by 16 feet has an abnormal height of 60 feet. This chimney like room encloses very annoying and depressing space.