Why the change to compact crank sets? Because amateurs tend to use what the pros use. Since pro riders have not so easily been able to rely on "chemical assistance" to help their performance, speeds have fallen, and so has the necessity of the gearing necessary to achieve these speeds. Riders in the late 90's were flying on race courses using metal bikes with 16 and 18 speed drivelines quite a bit faster than they are today with carbon fiber bikes running 22 and 24 speed drivelines. For ordinary mortals a 50 tooth chainring is enough.