Wouldn't breaking their wrists make doing whatever job he wants them to do harder?
But then, Pruneface was also a Nazi spy. The Nazis in Dick Tracy were not bright, though they were vicious(try MRS. Pruneface sometime, much worse than her dead hubby): they seemed to pick the most glaringly attention-getting dudes in Germany to do their espionage. (Usually guys with freakishly wrinkly faces)