More that the frame is softer and more wear prone then a steel cable. I've seen very few cables break at the BB port, and seen very few frames with serious damage from a cable. What we do see often enough are grime getting onto the cable and causing more friction and in time BB guide wear. But cables and guides are fairly low cost and easily replaced. I do agree that this cable routing isn't the best. Some frames have some sort of liner or tube that contains the cable as it goes through the BB area. Andy