The stethoscope is not unused, but it is generally not needed. If a patient's cardiopulmonary function really has an issue, they'll call for a consultation from cardiology or thoracic surgery to handle it. When it's an emergency, the scalpel comes into play.
Internal medicine doctors always carry stethoscopes; there's no choice, as clinical needs require it. Surgery emphasizes swift and decisive action. In internal medicine, there's usually more time to care for patients comprehensively in the ward compared to surgery. Frequently listening to the patient's cardiopulmonary function is never a bad idea.
A similar distinction lies in the white coat. Surgical white coats tend to be dirtier than those of internal medicine doctors. On TV, white coats are often portrayed as fashionable trench coats for posturing, but their real purpose is like a chef's apron—to prevent contamination from dirty materials spilling onto the doctor's personal clothing.